diff --git a/src/analyzer/Analyzer.cc b/src/analyzer/Analyzer.cc
index 6f109c4b72..dd21861125 100644
--- a/src/analyzer/Analyzer.cc
+++ b/src/analyzer/Analyzer.cc
@@ -124,11 +124,11 @@ void Analyzer::CtorInit(const Tag& arg_tag, Connection* arg_conn)
 	skip = false;
 	finished = false;
 	removing = false;
-	parent = 0;
-	orig_supporters = 0;
-	resp_supporters = 0;
-	signature = 0;
-	output_handler = 0;
+	parent = nullptr;
+	orig_supporters = nullptr;
+	resp_supporters = nullptr;
+	signature = nullptr;
+	output_handler = nullptr;
 	}
 
 Analyzer::~Analyzer()
@@ -138,7 +138,7 @@ Analyzer::~Analyzer()
 	LOOP_OVER_CHILDREN(i)
 		delete *i;
 
-	SupportAnalyzer* next = 0;
+	SupportAnalyzer* next = nullptr;
 
 	for ( SupportAnalyzer* a = orig_supporters; a; a = next )
 		{
@@ -501,7 +501,7 @@ Analyzer* Analyzer::FindChild(ID arg_id)
 			return child;
 		}
 
-	return 0;
+	return nullptr;
 	}
 
 Analyzer* Analyzer::FindChild(Tag arg_tag)
@@ -523,13 +523,13 @@ Analyzer* Analyzer::FindChild(Tag arg_tag)
 			return child;
 		}
 
-	return 0;
+	return nullptr;
 	}
 
 Analyzer* Analyzer::FindChild(const char* name)
 	{
 	Tag tag = analyzer_mgr->GetComponentTag(name);
-	return tag ? FindChild(tag) : 0;
+	return tag ? FindChild(tag) : nullptr;
 	}
 
 void Analyzer::DeleteChild(analyzer_list::iterator i)
@@ -570,7 +570,7 @@ void Analyzer::AddSupportAnalyzer(SupportAnalyzer* analyzer)
 		analyzer->IsOrig() ? &orig_supporters : &resp_supporters;
 
 	// Find end of the list.
-	SupportAnalyzer* prev = 0;
+	SupportAnalyzer* prev = nullptr;
 	SupportAnalyzer* s;
 	for ( s = *head; s; prev = s, s = s->sibling )
 		;
@@ -621,7 +621,7 @@ SupportAnalyzer* Analyzer::FirstSupportAnalyzer(bool orig)
 	SupportAnalyzer* sa = orig ? orig_supporters : resp_supporters;
 
 	if ( ! sa )
-		return 0;
+		return nullptr;
 
 	if ( ! sa->Removing() )
 		return sa;
@@ -922,7 +922,7 @@ void TransportLayerAnalyzer::SetContentsFile(unsigned int /* direction */,
 BroFile* TransportLayerAnalyzer::GetContentsFile(unsigned int /* direction */) const
 	{
 	reporter->Error("analyzer type does not support writing to a contents file");
-	return 0;
+	return nullptr;
 	}
 
 void TransportLayerAnalyzer::PacketContents(const u_char* data, int len)
diff --git a/src/analyzer/Analyzer.h b/src/analyzer/Analyzer.h
index 4d25fccb27..a4bd7b7a20 100644
--- a/src/analyzer/Analyzer.h
+++ b/src/analyzer/Analyzer.h
@@ -152,7 +152,7 @@ public:
 	 * @param caplen The packet's capture length, if available.
 	 */
 	void NextPacket(int len, const u_char* data, bool is_orig,
-			uint64_t seq = -1, const IP_Hdr* ip = 0, int caplen = 0);
+			uint64_t seq = -1, const IP_Hdr* ip = nullptr, int caplen = 0);
 
 	/**
 	 * Passes stream input to the analyzer for processing. The analyzer
@@ -528,7 +528,7 @@ public:
 	 * @param len If \a data is given, the length of it.
 	 */
 	virtual void ProtocolViolation(const char* reason,
-					const char* data = 0, int len = 0);
+					const char* data = nullptr, int len = 0);
 
 	/**
 	 * Returns true if ProtocolConfirmation() has been called at least
@@ -558,13 +558,13 @@ public:
 	 * Convenience function that forwards directly to the corresponding
 	 * Connection::Event().
 	 */
-	void Event(EventHandlerPtr f, const char* name = 0);
+	void Event(EventHandlerPtr f, const char* name = nullptr);
 
 	/**
 	 * Convenience function that forwards directly to the corresponding
 	 * Connection::Event().
 	 */
-	void Event(EventHandlerPtr f, Val* v1, Val* v2 = 0);
+	void Event(EventHandlerPtr f, Val* v1, Val* v2 = nullptr);
 
 	/**
 	 * Convenience function that forwards directly to
@@ -796,7 +796,7 @@ public:
 	 * connection originator side, and otherwise for the responder side.
 	 */
 	SupportAnalyzer(const char* name, Connection* conn, bool arg_orig)
-		: Analyzer(name, conn)	{ orig = arg_orig; sibling = 0; }
+		: Analyzer(name, conn)	{ orig = arg_orig; sibling = nullptr; }
 
 	/**
 	 * Destructor.
@@ -879,7 +879,7 @@ public:
 	 * @param conn The connection the analyzer is associated with.
 	 */
 	TransportLayerAnalyzer(const char* name, Connection* conn)
-		: Analyzer(name, conn)	{ pia = 0; }
+		: Analyzer(name, conn)	{ pia = nullptr; }
 
 	/**
 	 * Overridden from parent class.
diff --git a/src/analyzer/Manager.cc b/src/analyzer/Manager.cc
index 667f371407..948e2d09b2 100644
--- a/src/analyzer/Manager.cc
+++ b/src/analyzer/Manager.cc
@@ -292,17 +292,17 @@ Analyzer* Manager::InstantiateAnalyzer(const Tag& tag, Connection* conn)
 	if ( ! c )
 		{
 		reporter->InternalWarning("request to instantiate unknown analyzer");
-		return 0;
+		return nullptr;
 		}
 
 	if ( ! c->Enabled() )
-		return 0;
+		return nullptr;
 
 	if ( ! c->Factory() )
 		{
 		reporter->InternalWarning("analyzer %s cannot be instantiated dynamically",
 					  GetComponentName(tag).c_str());
-		return 0;
+		return nullptr;
 		}
 
 	Analyzer* a = c->Factory()(conn);
@@ -310,7 +310,7 @@ Analyzer* Manager::InstantiateAnalyzer(const Tag& tag, Connection* conn)
 	if ( ! a )
 		{
 		reporter->InternalWarning("analyzer instantiation failed");
-		return 0;
+		return nullptr;
 		}
 
 	a->SetAnalyzerTag(tag);
@@ -321,12 +321,12 @@ Analyzer* Manager::InstantiateAnalyzer(const Tag& tag, Connection* conn)
 Analyzer* Manager::InstantiateAnalyzer(const char* name, Connection* conn)
 	{
 	Tag tag = GetComponentTag(name);
-	return tag ? InstantiateAnalyzer(tag, conn) : 0;
+	return tag ? InstantiateAnalyzer(tag, conn) : nullptr;
 	}
 
 Manager::tag_set* Manager::LookupPort(TransportProto proto, uint32_t port, bool add_if_not_found)
 	{
-	analyzer_map_by_port* m = 0;
+	analyzer_map_by_port* m = nullptr;
 
 	switch ( proto ) {
 	case TRANSPORT_TCP:
@@ -339,7 +339,7 @@ Manager::tag_set* Manager::LookupPort(TransportProto proto, uint32_t port, bool
 
 	default:
 		reporter->InternalWarning("unsupported transport protocol in analyzer::Manager::LookupPort");
-		return 0;
+		return nullptr;
 	}
 
 	analyzer_map_by_port::const_iterator i = m->find(port);
@@ -348,7 +348,7 @@ Manager::tag_set* Manager::LookupPort(TransportProto proto, uint32_t port, bool
 		return i->second;
 
 	if ( ! add_if_not_found )
-		return 0;
+		return nullptr;
 
 	tag_set* l = new tag_set;
 	m->insert(std::make_pair(port, l));
@@ -362,11 +362,11 @@ Manager::tag_set* Manager::LookupPort(PortVal* val, bool add_if_not_found)
 
 bool Manager::BuildInitialAnalyzerTree(Connection* conn)
 	{
-	tcp::TCP_Analyzer* tcp = 0;
-	udp::UDP_Analyzer* udp = 0;
-	icmp::ICMP_Analyzer* icmp = 0;
-	TransportLayerAnalyzer* root = 0;
-	pia::PIA* pia = 0;
+	tcp::TCP_Analyzer* tcp = nullptr;
+	udp::UDP_Analyzer* udp = nullptr;
+	icmp::ICMP_Analyzer* icmp = nullptr;
+	TransportLayerAnalyzer* root = nullptr;
+	pia::PIA* pia = nullptr;
 	bool check_port = false;
 
 	switch ( conn->ConnTransport() ) {
@@ -628,7 +628,7 @@ bool Manager::ApplyScheduledAnalyzers(Connection* conn, bool init, TransportLaye
 
 		EnumVal* tag = it->AsEnumVal();
 		Ref(tag);
-		conn->Event(scheduled_analyzer_applied, 0, tag);
+		conn->Event(scheduled_analyzer_applied, nullptr, tag);
 
 		DBG_ANALYZER_ARGS(conn, "activated %s analyzer as scheduled",
 		                  analyzer_mgr->GetComponentName(*it).c_str());
diff --git a/src/analyzer/Manager.h b/src/analyzer/Manager.h
index fe32e43be9..084f4535fb 100644
--- a/src/analyzer/Manager.h
+++ b/src/analyzer/Manager.h
@@ -311,7 +311,7 @@ public:
 	 *
 	 * @return True if at least one scheduled analyzer was found.
 	 */
-	bool ApplyScheduledAnalyzers(Connection* conn, bool init_and_event = true, TransportLayerAnalyzer* parent = 0);
+	bool ApplyScheduledAnalyzers(Connection* conn, bool init_and_event = true, TransportLayerAnalyzer* parent = nullptr);
 
 	/**
 	 * Schedules a particular analyzer for an upcoming connection. Once
diff --git a/src/analyzer/protocol/bittorrent/BitTorrentTracker.cc b/src/analyzer/protocol/bittorrent/BitTorrentTracker.cc
index 7b0d8aedbb..d4ee18edab 100644
--- a/src/analyzer/protocol/bittorrent/BitTorrentTracker.cc
+++ b/src/analyzer/protocol/bittorrent/BitTorrentTracker.cc
@@ -15,7 +15,7 @@
 
 using namespace analyzer::bittorrent;
 
-static TableType* bt_tracker_headers = 0;
+static TableType* bt_tracker_headers = nullptr;
 static RecordType* bittorrent_peer;
 static TableType* bittorrent_peer_set;
 static RecordType* bittorrent_benc_value;
@@ -44,7 +44,7 @@ BitTorrentTracker_Analyzer::BitTorrentTracker_Analyzer(Connection* c)
 	req_buf[sizeof(req_buf) - 1] = 0;
 	req_buf_pos = req_buf;
 	req_buf_len = 0;
-	req_val_uri = 0;
+	req_val_uri = nullptr;
 	req_val_headers = new TableVal({NewRef{}, bt_tracker_headers});
 
 	res_state = BTT_RES_STATUS;
@@ -230,16 +230,16 @@ void BitTorrentTracker_Analyzer::InitBencParser(void)
 	benc_count.clear();
 
 	benc_state = BENC_STATE_EMPTY;
-	benc_raw = 0;
+	benc_raw = nullptr;
 	benc_raw_type = BENC_TYPE_NONE;
 	benc_raw_len = 0;
-	benc_key = 0;
+	benc_key = nullptr;
 	benc_key_len = 0;
-	benc_strlen = 0;
-	benc_str = 0;
+	benc_strlen = nullptr;
+	benc_str = nullptr;
 	benc_str_len = 0;
 	benc_str_have = 0;
-	benc_int = 0;
+	benc_int = nullptr;
 	benc_int_val = 0;
 	}
 
@@ -353,8 +353,8 @@ void BitTorrentTracker_Analyzer::EmitRequest(void)
 			IntrusivePtr{AdoptRef{}, req_val_headers}
 		);
 
-	req_val_uri = 0;
-	req_val_headers = 0;
+	req_val_uri = nullptr;
+	req_val_headers = nullptr;
 	}
 
 bool BitTorrentTracker_Analyzer::ParseResponse(char* line)
@@ -406,7 +406,7 @@ bool BitTorrentTracker_Analyzer::ParseResponse(char* line)
 						IntrusivePtr{AdoptRef{}, val_mgr->GetCount(res_status)},
 						IntrusivePtr{AdoptRef{}, res_val_headers}
 					);
-				res_val_headers = 0;
+				res_val_headers = nullptr;
 				res_buf_pos = res_buf + res_buf_len;
 				res_state = BTT_RES_DONE;
 				}
@@ -481,7 +481,7 @@ void BitTorrentTracker_Analyzer::ResponseBenc(int name_len, char* name,
 			RecordVal* peer = new RecordVal(bittorrent_peer);
 			peer->Assign(0, make_intrusive<AddrVal>(ad));
 			peer->Assign(1, val_mgr->GetPort(pt, TRANSPORT_TCP));
-			res_val_peers->Assign(peer, 0);
+			res_val_peers->Assign(peer, nullptr);
 
 			Unref(peer);
 			}
@@ -617,9 +617,9 @@ int BitTorrentTracker_Analyzer::ResponseParseBenc(void)
 					ResponseBenc(benc_key_len, benc_key,
 							benc_raw_type,
 							benc_raw_len, benc_raw);
-					benc_key = 0;
+					benc_key = nullptr;
 					benc_key_len = 0;
-					benc_raw = 0;
+					benc_raw = nullptr;
 					benc_raw_len = 0;
 					benc_raw_type = BENC_TYPE_NONE;
 					}
@@ -686,7 +686,7 @@ int BitTorrentTracker_Analyzer::ResponseParseBenc(void)
 						ResponseBenc(benc_key_len,
 							benc_key, BENC_TYPE_INT,
 							benc_int_val);
-						benc_key = 0;
+						benc_key = nullptr;
 						benc_key_len = 0;
 						}
 					}
@@ -764,7 +764,7 @@ int BitTorrentTracker_Analyzer::ResponseParseBenc(void)
 							BENC_TYPE_STR,
 							benc_str_len, benc_str);
 					benc_key_len = 0;
-					benc_key = 0;
+					benc_key = nullptr;
 					}
 
 				if ( ! benc_str_len )
@@ -796,7 +796,7 @@ void BitTorrentTracker_Analyzer::EmitResponse(void)
 			IntrusivePtr{AdoptRef{}, res_val_benc}
 		);
 
-	res_val_headers = 0;
-	res_val_peers = 0;
-	res_val_benc = 0;
+	res_val_headers = nullptr;
+	res_val_peers = nullptr;
+	res_val_benc = nullptr;
 	}
diff --git a/src/analyzer/protocol/conn-size/functions.bif b/src/analyzer/protocol/conn-size/functions.bif
index f74464aef9..f6da9c61a8 100644
--- a/src/analyzer/protocol/conn-size/functions.bif
+++ b/src/analyzer/protocol/conn-size/functions.bif
@@ -7,7 +7,7 @@ static analyzer::Analyzer* GetConnsizeAnalyzer(Val* cid)
 	{
 	Connection* c = sessions->FindConnection(cid);
 	if ( ! c )
-		return 0;
+		return nullptr;
 
 	analyzer::Analyzer* a = c->FindAnalyzer("CONNSIZE");
 	if ( ! a )
diff --git a/src/analyzer/protocol/dns/DNS.cc b/src/analyzer/protocol/dns/DNS.cc
index 8ad9d796ce..5c041a09d8 100644
--- a/src/analyzer/protocol/dns/DNS.cc
+++ b/src/analyzer/protocol/dns/DNS.cc
@@ -545,7 +545,7 @@ bool DNS_Interpreter::ParseRR_Name(DNS_MsgInfo* msg,
 
 		default:
 			analyzer->Conn()->Internal("DNS_RR_bad_name");
-			reply_event = 0;
+			reply_event = nullptr;
 	}
 
 	if ( reply_event && ! msg->skip_event )
@@ -757,7 +757,7 @@ bool DNS_Interpreter::ParseRR_TSIG(DNS_MsgInfo* msg,
 	ExtractOctets(data, len, dns_TSIG_addl ? &request_MAC : nullptr);
 	unsigned int orig_id = ExtractShort(data, len);
 	unsigned int rr_error = ExtractShort(data, len);
-	ExtractOctets(data, len, 0);  // Other Data
+	ExtractOctets(data, len, nullptr);  // Other Data
 
 	if ( dns_TSIG_addl )
 		{
@@ -1256,7 +1256,7 @@ static StringVal* extract_char_string(analyzer::Analyzer* analyzer,
                                       const u_char*& data, int& len, int& rdlen)
 	{
 	if ( rdlen <= 0 )
-		return 0;
+		return nullptr;
 
 	uint8_t str_size = data[0];
 
@@ -1267,7 +1267,7 @@ static StringVal* extract_char_string(analyzer::Analyzer* analyzer,
 	if ( str_size > rdlen )
 		{
 		analyzer->Weird("DNS_TXT_char_str_past_rdlen");
-		return 0;
+		return nullptr;
 		}
 
 	StringVal* rval = new StringVal(str_size,
@@ -1428,7 +1428,7 @@ DNS_MsgInfo::DNS_MsgInfo(DNS_RawMsgHdr* hdr, int arg_is_query)
 	id = ntohs(hdr->id);
 	is_query = arg_is_query;
 
-	query_name = 0;
+	query_name = nullptr;
 	atype = TYPE_ALL;
 	aclass = 0;
 	ttl = 0;
@@ -1612,7 +1612,7 @@ Contents_DNS::Contents_DNS(Connection* conn, bool orig,
 	{
 	interp = arg_interp;
 
-	msg_buf = 0;
+	msg_buf = nullptr;
 	buf_n = buf_len = msg_size = 0;
 	state = DNS_LEN_HI;
 	}
@@ -1685,7 +1685,7 @@ void Contents_DNS::DeliverStream(int len, const u_char* data, bool orig)
 		// Haven't filled up the message buffer yet, no more to do.
 		return;
 
-	ForwardPacket(msg_size, msg_buf, orig, -1, 0, 0);
+	ForwardPacket(msg_size, msg_buf, orig, -1, nullptr, 0);
 
 	buf_n = 0;
 	state = DNS_LEN_HI;
@@ -1699,7 +1699,7 @@ DNS_Analyzer::DNS_Analyzer(Connection* conn)
 : tcp::TCP_ApplicationAnalyzer("DNS", conn)
 	{
 	interp = new DNS_Interpreter(this);
-	contents_dns_orig = contents_dns_resp = 0;
+	contents_dns_orig = contents_dns_resp = nullptr;
 
 	if ( Conn()->ConnTransport() == TRANSPORT_TCP )
 		{
diff --git a/src/analyzer/protocol/dns/Plugin.cc b/src/analyzer/protocol/dns/Plugin.cc
index 4aa46499c0..4aceaf0ff4 100644
--- a/src/analyzer/protocol/dns/Plugin.cc
+++ b/src/analyzer/protocol/dns/Plugin.cc
@@ -12,7 +12,7 @@ public:
 	plugin::Configuration Configure() override
 		{
 		AddComponent(new ::analyzer::Component("DNS", ::analyzer::dns::DNS_Analyzer::Instantiate));
-		AddComponent(new ::analyzer::Component("Contents_DNS", 0));
+		AddComponent(new ::analyzer::Component("Contents_DNS", nullptr));
 
 		plugin::Configuration config;
 		config.name = "Zeek::DNS";
diff --git a/src/analyzer/protocol/finger/Finger.cc b/src/analyzer/protocol/finger/Finger.cc
index 1beba6947d..6fa54964a3 100644
--- a/src/analyzer/protocol/finger/Finger.cc
+++ b/src/analyzer/protocol/finger/Finger.cc
@@ -60,7 +60,7 @@ void Finger_Analyzer::DeliverStream(int length, const u_char* data, bool is_orig
 		assert(line <= end_of_line);
 		size_t n = end_of_line >= line ? end_of_line - line : 0; // just to be sure if assertions aren't on.
 		const char* at = reinterpret_cast<const char*>(memchr(line, '@', n));
-		const char* host = 0;
+		const char* host = nullptr;
 		if ( ! at )
 			at = host = end_of_line;
 		else
diff --git a/src/analyzer/protocol/ftp/FTP.cc b/src/analyzer/protocol/ftp/FTP.cc
index 7957bb01be..31eaa481d1 100644
--- a/src/analyzer/protocol/ftp/FTP.cc
+++ b/src/analyzer/protocol/ftp/FTP.cc
@@ -204,7 +204,7 @@ void FTP_ADAT_Analyzer::DeliverStream(int len, const u_char* data, bool orig)
 	const char* line = (const char*) data;
 	const char* end_of_line = line + len;
 
-	BroString* decoded_adat = 0;
+	BroString* decoded_adat = nullptr;
 
 	if ( orig )
 		{
@@ -217,7 +217,7 @@ void FTP_ADAT_Analyzer::DeliverStream(int len, const u_char* data, bool orig)
 			{
 			line = skip_whitespace(line + cmd_len, end_of_line);
 			StringVal encoded(end_of_line - line, line);
-			decoded_adat = decode_base64(encoded.AsString(), 0, Conn());
+			decoded_adat = decode_base64(encoded.AsString(), nullptr, Conn());
 
 			if ( first_token )
 				{
@@ -247,7 +247,7 @@ void FTP_ADAT_Analyzer::DeliverStream(int len, const u_char* data, bool orig)
 					// Doesn't look like TLS/SSL, so done analyzing.
 					done = true;
 					delete decoded_adat;
-					decoded_adat = 0;
+					decoded_adat = nullptr;
 					}
 				}
 
@@ -292,7 +292,7 @@ void FTP_ADAT_Analyzer::DeliverStream(int len, const u_char* data, bool orig)
 				{
 				line += 5;
 				StringVal encoded(end_of_line - line, line);
-				decoded_adat = decode_base64(encoded.AsString(), 0, Conn());
+				decoded_adat = decode_base64(encoded.AsString(), nullptr, Conn());
 				}
 
 			break;
diff --git a/src/analyzer/protocol/ftp/Plugin.cc b/src/analyzer/protocol/ftp/Plugin.cc
index 49eef6c281..b7743355a7 100644
--- a/src/analyzer/protocol/ftp/Plugin.cc
+++ b/src/analyzer/protocol/ftp/Plugin.cc
@@ -12,7 +12,7 @@ public:
 	plugin::Configuration Configure() override
 		{
 		AddComponent(new ::analyzer::Component("FTP", ::analyzer::ftp::FTP_Analyzer::Instantiate));
-		AddComponent(new ::analyzer::Component("FTP_ADAT", 0));
+		AddComponent(new ::analyzer::Component("FTP_ADAT", nullptr));
 
 		plugin::Configuration config;
 		config.name = "Zeek::FTP";
diff --git a/src/analyzer/protocol/gnutella/Gnutella.cc b/src/analyzer/protocol/gnutella/Gnutella.cc
index e22a5ad755..a6d36218c8 100644
--- a/src/analyzer/protocol/gnutella/Gnutella.cc
+++ b/src/analyzer/protocol/gnutella/Gnutella.cc
@@ -40,7 +40,7 @@ Gnutella_Analyzer::Gnutella_Analyzer(Connection* conn)
 	new_state = 0;
 	sent_establish = 0;
 
-	ms = 0;
+	ms = nullptr;
 
 	orig_msg_state = new GnutellaMsgState();
 	resp_msg_state = new GnutellaMsgState();
diff --git a/src/analyzer/protocol/http/HTTP.cc b/src/analyzer/protocol/http/HTTP.cc
index 14eab65ddc..8b1cf4c415 100644
--- a/src/analyzer/protocol/http/HTTP.cc
+++ b/src/analyzer/protocol/http/HTTP.cc
@@ -48,7 +48,7 @@ HTTP_Entity::HTTP_Entity(HTTP_Message *arg_message, MIME_Entity* parent_entity,
 	header_length = 0;
 	deliver_body = true;
 	encoding = IDENTITY;
-	zip = 0;
+	zip = nullptr;
 	is_partial_content = false;
 	offset = 0;
 	instance_length = -1; // unspecified
@@ -67,7 +67,7 @@ void HTTP_Entity::EndOfData()
 		{
 		zip->Done();
 		delete zip;
-		zip = 0;
+		zip = nullptr;
 		encoding = IDENTITY;
 		}
 
@@ -114,7 +114,7 @@ void HTTP_Entity::Deliver(int len, const char* data, bool trailing_CRLF)
 		switch ( chunked_transfer_state ) {
 		case EXPECT_CHUNK_SIZE:
 			ASSERT(trailing_CRLF);
-			if ( ! atoi_n(len, data, 0, 16, expect_data_length) )
+			if ( ! atoi_n(len, data, nullptr, 16, expect_data_length) )
 				{
 				http_message->Weird("HTTP_bad_chunk_size");
 				expect_data_length = 0;
@@ -365,7 +365,7 @@ void HTTP_Entity::SubmitHeader(mime::MIME_Header* h)
 		if ( ! mime::is_null_data_chunk(vt) )
 			{
 			int64_t n;
-			if ( atoi_n(vt.length, vt.data, 0, 10, n) )
+			if ( atoi_n(vt.length, vt.data, nullptr, 10, n) )
 				{
 				content_length = n;
 
@@ -427,8 +427,8 @@ void HTTP_Entity::SubmitHeader(mime::MIME_Header* h)
 		              instance_length_str.c_str());
 
 		int64_t f, l;
-		atoi_n(first_byte_pos.size(), first_byte_pos.c_str(), 0, 10, f);
-		atoi_n(last_byte_pos.size(), last_byte_pos.c_str(), 0, 10, l);
+		atoi_n(first_byte_pos.size(), first_byte_pos.c_str(), nullptr, 10, f);
+		atoi_n(last_byte_pos.size(), last_byte_pos.c_str(), nullptr, 10, l);
 		int64_t len = l - f + 1;
 
 		if ( DEBUG_http )
@@ -439,7 +439,7 @@ void HTTP_Entity::SubmitHeader(mime::MIME_Header* h)
 			if ( instance_length_str != "*" )
 				{
 				if ( ! atoi_n(instance_length_str.size(),
-				              instance_length_str.c_str(), 0, 10,
+				              instance_length_str.c_str(), nullptr, 10,
 				              instance_length) )
 					instance_length = 0;
 				}
@@ -596,9 +596,9 @@ HTTP_Message::HTTP_Message(HTTP_Analyzer* arg_analyzer,
 	content_line = arg_cl;
 	is_orig = arg_is_orig;
 
-	current_entity = 0;
-	top_level = new HTTP_Entity(this, 0, expect_body);
-	entity_data_buffer = 0;
+	current_entity = nullptr;
+	top_level = new HTTP_Entity(this, nullptr, expect_body);
+	entity_data_buffer = nullptr;
 	BeginEntity(top_level);
 
 	start_time = network_time;
@@ -837,20 +837,20 @@ HTTP_Analyzer::HTTP_Analyzer(Connection* conn)
 	keep_alive = 0;
 	connection_close = 0;
 
-	request_message = reply_message = 0;
+	request_message = reply_message = nullptr;
 	request_state = EXPECT_REQUEST_LINE;
 	reply_state = EXPECT_REPLY_LINE;
 
 	request_ongoing = 0;
-	request_method = request_URI = 0;
-	unescaped_URI = 0;
+	request_method = request_URI = nullptr;
+	unescaped_URI = nullptr;
 
 	reply_ongoing = 0;
 	reply_code = 0;
-	reply_reason_phrase = 0;
+	reply_reason_phrase = nullptr;
 
 	connect_request = false;
-	pia = 0;
+	pia = nullptr;
 	upgraded = false;
 	upgrade_connection = false;
 	upgrade_protocol.clear();
@@ -882,10 +882,10 @@ void HTTP_Analyzer::Done()
 	ReplyMade(true, "message interrupted when connection done");
 
 	delete request_message;
-	request_message = 0;
+	request_message = nullptr;
 
 	delete reply_message;
-	reply_message = 0;
+	reply_message = nullptr;
 
 	GenStats();
 
@@ -1061,8 +1061,8 @@ void HTTP_Analyzer::DeliverStream(int len, const u_char* data, bool is_orig)
 
 				if ( AddChildAnalyzer(pia) )
 					{
-					pia->FirstPacket(true, 0);
-					pia->FirstPacket(false, 0);
+					pia->FirstPacket(true, nullptr);
+					pia->FirstPacket(false, nullptr);
 
 					// This connection has transitioned to no longer
 					// being http and the content line support analyzers
@@ -1073,7 +1073,7 @@ void HTTP_Analyzer::DeliverStream(int len, const u_char* data, bool is_orig)
 
 				else
 					// AddChildAnalyzer() will have deleted PIA.
-					pia = 0;
+					pia = nullptr;
 				}
 
 			break;
@@ -1193,7 +1193,7 @@ const char* HTTP_Analyzer::PrefixMatch(const char* line,
 
 	if ( *prefix )
 		// It didn't match.
-		return 0;
+		return nullptr;
 
 	return line;
 	}
@@ -1201,15 +1201,15 @@ const char* HTTP_Analyzer::PrefixMatch(const char* line,
 const char* HTTP_Analyzer::PrefixWordMatch(const char* line,
 				const char* end_of_line, const char* prefix)
 	{
-	if ( (line = PrefixMatch(line, end_of_line, prefix)) == 0 )
-		return 0;
+	if ( (line = PrefixMatch(line, end_of_line, prefix)) == nullptr )
+		return nullptr;
 
 	const char* orig_line = line;
 	line = skip_whitespace(line, end_of_line);
 
 	if ( line == orig_line )
 		// Word didn't end at prefix.
-		return 0;
+		return nullptr;
 
 	return line;
 	}
@@ -1235,7 +1235,7 @@ static const char* get_HTTP_token(const char* s, const char* e)
 
 int HTTP_Analyzer::HTTP_RequestLine(const char* line, const char* end_of_line)
 	{
-	const char* rest = 0;
+	const char* rest = nullptr;
 	const char* end_of_method = get_HTTP_token(line, end_of_line);
 
 	if ( end_of_method == line )
@@ -1439,7 +1439,7 @@ void HTTP_Analyzer::HTTP_Reply()
 	else
 		{
 		Unref(reply_reason_phrase);
-		reply_reason_phrase = 0;
+		reply_reason_phrase = nullptr;
 		}
 	}
 
@@ -1459,7 +1459,7 @@ void HTTP_Analyzer::RequestMade(bool interrupted, const char* msg)
 	Unref(unescaped_URI);
 	Unref(request_URI);
 
-	request_method = request_URI = unescaped_URI = 0;
+	request_method = request_URI = unescaped_URI = nullptr;
 
 	num_request_lines = 0;
 
@@ -1492,7 +1492,7 @@ void HTTP_Analyzer::ReplyMade(bool interrupted, const char* msg)
 	if ( reply_reason_phrase )
 		{
 		Unref(reply_reason_phrase);
-		reply_reason_phrase = 0;
+		reply_reason_phrase = nullptr;
 		}
 
 	// unanswered requests = 1 because there is no pop after 101.
@@ -1531,7 +1531,7 @@ void HTTP_Analyzer::RequestClash(Val* /* clash_val */)
 
 const BroString* HTTP_Analyzer::UnansweredRequestMethod()
 	{
-	return unanswered_requests.empty() ? 0 : unanswered_requests.front()->AsString();
+	return unanswered_requests.empty() ? nullptr : unanswered_requests.front()->AsString();
 	}
 
 int HTTP_Analyzer::HTTP_ReplyLine(const char* line, const char* end_of_line)
diff --git a/src/analyzer/protocol/icmp/ICMP.cc b/src/analyzer/protocol/icmp/ICMP.cc
index 59e8d93909..552f87c947 100644
--- a/src/analyzer/protocol/icmp/ICMP.cc
+++ b/src/analyzer/protocol/icmp/ICMP.cc
@@ -81,7 +81,7 @@ void ICMP_Analyzer::DeliverPacket(int len, const u_char* data,
 	if ( rule_matcher )
 		{
 		if ( ! matcher_state.MatcherInitialized(is_orig) )
-			matcher_state.InitEndpointMatcher(this, ip, len, is_orig, 0);
+			matcher_state.InitEndpointMatcher(this, ip, len, is_orig, nullptr);
 		}
 
 	type = icmpp->icmp_type;
@@ -497,7 +497,7 @@ void ICMP_Analyzer::Echo(double t, const struct icmp* icmpp, int len,
 					 int caplen, const u_char*& data, const IP_Hdr* ip_hdr)
 	{
 	// For handling all Echo related ICMP messages
-	EventHandlerPtr f = 0;
+	EventHandlerPtr f = nullptr;
 
 	if ( ip_hdr->NextProto() == IPPROTO_ICMPV6 )
 		f = (icmpp->icmp_type == ICMP6_ECHO_REQUEST)
@@ -658,7 +658,7 @@ void ICMP_Analyzer::RouterSolicit(double t, const struct icmp* icmpp, int len,
 void ICMP_Analyzer::Context4(double t, const struct icmp* icmpp,
 		int len, int caplen, const u_char*& data, const IP_Hdr* ip_hdr)
 	{
-	EventHandlerPtr f = 0;
+	EventHandlerPtr f = nullptr;
 
 	switch ( icmpp->icmp_type )
 		{
@@ -684,7 +684,7 @@ void ICMP_Analyzer::Context4(double t, const struct icmp* icmpp,
 void ICMP_Analyzer::Context6(double t, const struct icmp* icmpp,
 		int len, int caplen, const u_char*& data, const IP_Hdr* ip_hdr)
 	{
-	EventHandlerPtr f = 0;
+	EventHandlerPtr f = nullptr;
 
 	switch ( icmpp->icmp_type )
 		{
@@ -720,8 +720,8 @@ void ICMP_Analyzer::Context6(double t, const struct icmp* icmpp,
 
 VectorVal* ICMP_Analyzer::BuildNDOptionsVal(int caplen, const u_char* data)
 	{
-	static RecordType* icmp6_nd_option_type = 0;
-	static RecordType* icmp6_nd_prefix_info_type = 0;
+	static RecordType* icmp6_nd_option_type = nullptr;
+	static RecordType* icmp6_nd_prefix_info_type = nullptr;
 
 	if ( ! icmp6_nd_option_type )
 		{
diff --git a/src/analyzer/protocol/ident/Ident.cc b/src/analyzer/protocol/ident/Ident.cc
index 5417492f58..a9c6d5a066 100644
--- a/src/analyzer/protocol/ident/Ident.cc
+++ b/src/analyzer/protocol/ident/Ident.cc
@@ -52,7 +52,7 @@ void Ident_Analyzer::DeliverStream(int length, const u_char* data, bool is_orig)
 	const char* orig_line = line;
 	const char* end_of_line = line + length;
 
-	tcp::TCP_Endpoint* s = 0;
+	tcp::TCP_Endpoint* s = nullptr;
 
 	if ( TCP() )
 		s = is_orig ? TCP()->Orig() : TCP()->Resp();
@@ -194,17 +194,17 @@ const char* Ident_Analyzer::ParsePair(const char* line, const char* end_of_line,
 	line = ParsePort(line, end_of_line, p1);
 	if ( ! line )
 		{
-		return 0;
+		return nullptr;
 		}
 
 	if ( line >= end_of_line || line[0] != ',' )
-		return 0;
+		return nullptr;
 
 	++line;
 
 	line = ParsePort(line, end_of_line, p2);
 	if ( ! line )
-		return 0;
+		return nullptr;
 
 	return line;
 	}
@@ -216,7 +216,7 @@ const char* Ident_Analyzer::ParsePort(const char* line, const char* end_of_line,
 
 	line = skip_whitespace(line, end_of_line);
 	if ( ! isdigit(*line) )
-		return 0;
+		return nullptr;
 
 	const char* l = line;
 
diff --git a/src/analyzer/protocol/irc/IRC.cc b/src/analyzer/protocol/irc/IRC.cc
index ff9bb4cb4c..258ae51086 100644
--- a/src/analyzer/protocol/irc/IRC.cc
+++ b/src/analyzer/protocol/irc/IRC.cc
@@ -277,7 +277,7 @@ void IRC_Analyzer::DeliverStream(int length, const u_char* line, bool orig)
 				if ( parts[i][0] == '@' )
 					parts[i] = parts[i].substr(1);
 				auto idx = make_intrusive<StringVal>(parts[i].c_str());
-				set->Assign(idx.get(), 0);
+				set->Assign(idx.get(), nullptr);
 				}
 
 			EnqueueConnEvent(irc_names_info,
@@ -468,7 +468,7 @@ void IRC_Analyzer::DeliverStream(int length, const u_char* line, bool orig)
 			for ( unsigned int i = 0; i < parts.size(); ++i )
 				{
 				auto idx = make_intrusive<StringVal>(parts[i].c_str());
-				set->Assign(idx.get(), 0);
+				set->Assign(idx.get(), nullptr);
 				}
 
 			EnqueueConnEvent(irc_whois_channel_line,
@@ -857,7 +857,7 @@ void IRC_Analyzer::DeliverStream(int length, const u_char* line, bool orig)
 				info->Assign(2, make_intrusive<StringVal>(empty_string.c_str()));
 			// User mode.
 			info->Assign(3, make_intrusive<StringVal>(empty_string.c_str()));
-			list->Assign(info, 0);
+			list->Assign(info, nullptr);
 			Unref(info);
 			}
 
@@ -918,7 +918,7 @@ void IRC_Analyzer::DeliverStream(int length, const u_char* line, bool orig)
 			info->Assign(2, make_intrusive<StringVal>(empty_string.c_str()));
 			// User mode:
 			info->Assign(3, make_intrusive<StringVal>(mode.c_str()));
-			list->Assign(info.get(), 0);
+			list->Assign(info.get(), nullptr);
 			}
 
 		EnqueueConnEvent(irc_join_message,
@@ -957,7 +957,7 @@ void IRC_Analyzer::DeliverStream(int length, const u_char* line, bool orig)
 		for ( unsigned int i = 0; i < channelList.size(); ++i )
 			{
 			auto idx = make_intrusive<StringVal>(channelList[i].c_str());
-			set->Assign(idx.get(), 0);
+			set->Assign(idx.get(), nullptr);
 			}
 
 		EnqueueConnEvent(irc_part_message,
diff --git a/src/analyzer/protocol/login/Login.cc b/src/analyzer/protocol/login/Login.cc
index 39767ca420..d3dfee53f9 100644
--- a/src/analyzer/protocol/login/Login.cc
+++ b/src/analyzer/protocol/login/Login.cc
@@ -16,7 +16,7 @@
 
 using namespace analyzer::login;
 
-static RE_Matcher* re_skip_authentication = 0;
+static RE_Matcher* re_skip_authentication = nullptr;
 static RE_Matcher* re_direct_login_prompts;
 static RE_Matcher* re_login_prompts;
 static RE_Matcher* re_login_non_failure_msgs;
@@ -39,7 +39,7 @@ Login_Analyzer::Login_Analyzer(const char* name, Connection* conn)
 	user_text_first = 0;
 	user_text_last = MAX_USER_TEXT - 1;
 	num_user_text = 0;
-	client_name = username = 0;
+	client_name = username = nullptr;
 	saw_ploy = is_VMS = false;
 
 	if ( ! re_skip_authentication )
@@ -214,7 +214,7 @@ void Login_Analyzer::AuthenticationDialog(bool orig, char* line)
 			 // respect to it (see below).
 			 login_prompt_line != failure_line);
 
-		const char* next_prompt = 0;
+		const char* next_prompt = nullptr;
 		while ( (*prompt != '\0' &&
 			 (next_prompt = IsLoginPrompt(prompt + 1))) ||
 			multi_line_prompt )
@@ -507,7 +507,7 @@ const char* Login_Analyzer::IsLoginPrompt(const char* line) const
 	int prompt_match = re_login_prompts->MatchAnywhere(line);
 	if ( ! prompt_match || IsFailureMsg(line) )
 		// IRIX can report "login: ERROR: Login incorrect"
-		return 0;
+		return nullptr;
 
 	return &line[prompt_match];
 	}
@@ -565,7 +565,7 @@ char* Login_Analyzer::PeekUserText()
 		{
 		reporter->AnalyzerError(this,
 		  "underflow in Login_Analyzer::PeekUserText()");
-		return 0;
+		return nullptr;
 		}
 
 	return user_text[user_text_first];
@@ -576,7 +576,7 @@ char* Login_Analyzer::PopUserText()
 	char* s = PeekUserText();
 
 	if ( ! s )
-		return 0;
+		return nullptr;
 
 	if ( ++user_text_first == MAX_USER_TEXT )
 		user_text_first = 0;
diff --git a/src/analyzer/protocol/login/NVT.cc b/src/analyzer/protocol/login/NVT.cc
index 89295e1ac2..096adca591 100644
--- a/src/analyzer/protocol/login/NVT.cc
+++ b/src/analyzer/protocol/login/NVT.cc
@@ -320,7 +320,7 @@ char* TelnetEnvironmentOption::ExtractEnv(u_char*& data, int& len, int& code)
 
 	if ( code != ENVIRON_VAR && code != ENVIRON_VAL &&
 	     code != ENVIRON_USERVAR )
-		return 0;
+		return nullptr;
 
 	// Move past code.
 	--len;
@@ -338,7 +338,7 @@ char* TelnetEnvironmentOption::ExtractEnv(u_char*& data, int& len, int& code)
 			{
 			++d;	// move past ESC
 			if ( d >= data_end )
-				return 0;
+				return nullptr;
 			break;
 			}
 		}
@@ -400,7 +400,7 @@ TelnetOption* NVT_Analyzer::FindOption(unsigned int code)
 		if ( options[i]->Code() == code )
 			return options[i];
 
-	TelnetOption* opt = 0;
+	TelnetOption* opt = nullptr;
 	if ( i < NUM_TELNET_OPTIONS )
 		{ // Maybe we haven't created this option yet.
 		switch ( code ) {
diff --git a/src/analyzer/protocol/login/Plugin.cc b/src/analyzer/protocol/login/Plugin.cc
index aeedd5c04d..27457b04d7 100644
--- a/src/analyzer/protocol/login/Plugin.cc
+++ b/src/analyzer/protocol/login/Plugin.cc
@@ -17,10 +17,10 @@ public:
 		AddComponent(new ::analyzer::Component("Telnet", ::analyzer::login::Telnet_Analyzer::Instantiate));
 		AddComponent(new ::analyzer::Component("Rsh", ::analyzer::login::Rsh_Analyzer::Instantiate));
 		AddComponent(new ::analyzer::Component("Rlogin", ::analyzer::login::Rlogin_Analyzer::Instantiate));
-		AddComponent(new ::analyzer::Component("NVT", 0));
-		AddComponent(new ::analyzer::Component("Login", 0));
-		AddComponent(new ::analyzer::Component("Contents_Rsh", 0));
-		AddComponent(new ::analyzer::Component("Contents_Rlogin", 0));
+		AddComponent(new ::analyzer::Component("NVT", nullptr));
+		AddComponent(new ::analyzer::Component("Login", nullptr));
+		AddComponent(new ::analyzer::Component("Contents_Rsh", nullptr));
+		AddComponent(new ::analyzer::Component("Contents_Rlogin", nullptr));
 
 		plugin::Configuration config;
 		config.name = "Zeek::Login";
diff --git a/src/analyzer/protocol/login/Rlogin.cc b/src/analyzer/protocol/login/Rlogin.cc
index e041d757c9..244deb9cba 100644
--- a/src/analyzer/protocol/login/Rlogin.cc
+++ b/src/analyzer/protocol/login/Rlogin.cc
@@ -16,7 +16,7 @@ Contents_Rlogin_Analyzer::Contents_Rlogin_Analyzer(Connection* conn, bool orig,
 	{
 	num_bytes_to_scan = 0;
 	analyzer = arg_analyzer;
-	peer = 0;
+	peer = nullptr;
 
 	if ( orig )
 		state = save_state = RLOGIN_FIRST_NULL;
diff --git a/src/analyzer/protocol/mime/MIME.cc b/src/analyzer/protocol/mime/MIME.cc
index ea689733de..d644f00bb0 100644
--- a/src/analyzer/protocol/mime/MIME.cc
+++ b/src/analyzer/protocol/mime/MIME.cc
@@ -21,7 +21,7 @@
 
 namespace analyzer { namespace mime {
 
-static const data_chunk_t null_data_chunk = { 0, 0 };
+static const data_chunk_t null_data_chunk = { 0, nullptr };
 
 int mime_header_only = 0;
 int mime_decode_data = 1;
@@ -65,14 +65,14 @@ enum MIME_BOUNDARY_DELIMITER {
 static const char* MIMEHeaderName[] = {
 	"content-type",
 	"content-transfer-encoding",
-	0,
+	nullptr,
 };
 
 static const char* MIMEContentTypeName[] = {
 	"MULTIPART",
 	"MESSAGE",
 	"TEXT",
-	0,
+	nullptr,
 };
 
 static const char* MIMEContentSubtypeName[] = {
@@ -86,7 +86,7 @@ static const char* MIMEContentSubtypeName[] = {
 
 	"PLAIN",		// for text
 
-	0,			// other
+	nullptr,			// other
 };
 
 static const char* MIMEContentEncodingName[] = {
@@ -95,12 +95,12 @@ static const char* MIMEContentEncodingName[] = {
 	"BINARY",
 	"QUOTED-PRINTABLE",
 	"BASE64",
-	0,
+	nullptr,
 };
 
 bool is_null_data_chunk(data_chunk_t b)
 	{
-	return b.data == 0;
+	return b.data == nullptr;
 	}
 
 bool is_lws(char ch)
@@ -437,7 +437,7 @@ using namespace analyzer::mime;
 
 MIME_Multiline::MIME_Multiline()
 	{
-	line = 0;
+	line = nullptr;
 	}
 
 MIME_Multiline::~MIME_Multiline()
@@ -454,7 +454,7 @@ void MIME_Multiline::append(int len, const char* data)
 BroString* MIME_Multiline::get_concatenated_line()
 	{
 	if ( buffer.empty() )
-		return 0;
+		return nullptr;
 
 	delete line;
 	line = concatenate(buffer);
@@ -546,7 +546,7 @@ void MIME_Entity::init()
 	in_header = 1;
 	end_of_data = 0;
 
-	current_header_line = 0;
+	current_header_line = nullptr;
 	current_field_type = MIME_FIELD_OTHER;
 
 	need_to_parse_parameters = 0;
@@ -554,22 +554,22 @@ void MIME_Entity::init()
 	content_type_str = new StringVal("TEXT");
 	content_subtype_str = new StringVal("PLAIN");
 
-	content_encoding_str = 0;
-	multipart_boundary = 0;
+	content_encoding_str = nullptr;
+	multipart_boundary = nullptr;
 	content_type = CONTENT_TYPE_TEXT;
 	content_subtype = CONTENT_SUBTYPE_PLAIN;
 	content_encoding = CONTENT_ENCODING_OTHER;
 
-	parent = 0;
-	current_child_entity = 0;
+	parent = nullptr;
+	current_child_entity = nullptr;
 
-	base64_decoder = 0;
+	base64_decoder = nullptr;
 
 	data_buf_length = 0;
-	data_buf_data = 0;
+	data_buf_data = nullptr;
 	data_buf_offset = -1;
 
-	message = 0;
+	message = nullptr;
 	delay_adding_implicit_CRLF = false;
 	want_all_headers = false;
 	}
@@ -577,7 +577,7 @@ void MIME_Entity::init()
 MIME_Entity::~MIME_Entity()
 	{
 	if ( ! end_of_data )
-		reporter->AnalyzerError(message ? message->GetAnalyzer() : 0,
+		reporter->AnalyzerError(message ? message->GetAnalyzer() : nullptr,
 		            "missing MIME_Entity::EndOfData() before ~MIME_Entity");
 
 	delete current_header_line;
@@ -653,7 +653,7 @@ void MIME_Entity::EndOfData()
 
 	else
 		{
-		if ( current_child_entity != 0 )
+		if ( current_child_entity != nullptr )
 			{
 			if ( content_type == CONTENT_TYPE_MULTIPART )
 				IllegalFormat("multipart closing boundary delimiter missing");
@@ -675,13 +675,13 @@ void MIME_Entity::NewDataLine(int len, const char* data, bool trailing_CRLF)
 		{
 		switch ( CheckBoundaryDelimiter(len, data) ) {
 			case MULTIPART_BOUNDARY:
-				if ( current_child_entity != 0 )
+				if ( current_child_entity != nullptr )
 					EndChildEntity();
 				BeginChildEntity();
 				return;
 
 			case MULTIPART_CLOSING_BOUNDARY:
-				if ( current_child_entity != 0 )
+				if ( current_child_entity != nullptr )
 					EndChildEntity();
 				EndOfData();
 				return;
@@ -695,7 +695,7 @@ void MIME_Entity::NewDataLine(int len, const char* data, bool trailing_CRLF)
 		// binary encoding, and thus do not need to decode
 		// before passing the data to child.
 
-		if ( current_child_entity != 0 )
+		if ( current_child_entity != nullptr )
 			// Data before the first or after the last
 			// boundary delimiter are ignored
 			current_child_entity->Deliver(len, data, trailing_CRLF);
@@ -722,7 +722,7 @@ void MIME_Entity::NewHeader(int len, const char* data)
 
 void MIME_Entity::ContHeader(int len, const char* data)
 	{
-	if ( current_header_line == 0 )
+	if ( current_header_line == nullptr )
 		{
 		IllegalFormat("first header line starts with linear whitespace");
 
@@ -737,11 +737,11 @@ void MIME_Entity::ContHeader(int len, const char* data)
 
 void MIME_Entity::FinishHeader()
 	{
-	if ( current_header_line == 0 )
+	if ( current_header_line == nullptr )
 		return;
 
 	MIME_Header* h = new MIME_Header(current_header_line);
-	current_header_line = 0;
+	current_header_line = nullptr;
 
 	if ( ! is_null_data_chunk(h->get_name()) )
 		{
@@ -762,7 +762,7 @@ int MIME_Entity::LookupMIMEHeaderName(data_chunk_t name)
 	// A linear lookup should be fine for now.
 	// header names are case-insensitive (RFC 822, 2822, 2045).
 
-	for ( int i = 0; MIMEHeaderName[i] != 0; ++i )
+	for ( int i = 0; MIMEHeaderName[i] != nullptr; ++i )
 		if ( istrequal(name, MIMEHeaderName[i]) )
 			return i;
 	return -1;
@@ -770,7 +770,7 @@ int MIME_Entity::LookupMIMEHeaderName(data_chunk_t name)
 
 void MIME_Entity::ParseMIMEHeader(MIME_Header* h)
 	{
-	if ( h == 0 )
+	if ( h == nullptr )
 		return;
 
 	current_field_type = LookupMIMEHeaderName(h->get_name());
@@ -884,7 +884,7 @@ bool MIME_Entity::ParseFieldParameters(int len, const char* data)
 		data += offset;
 		len -= offset;
 
-		BroString* val = 0;
+		BroString* val = nullptr;
 
 		if ( current_field_type == MIME_CONTENT_TYPE &&
 		     content_type == CONTENT_TYPE_MULTIPART &&
@@ -1172,13 +1172,13 @@ void MIME_Entity::FinishDecodeBase64()
 		}
 
 	delete base64_decoder;
-	base64_decoder = 0;
+	base64_decoder = nullptr;
 	}
 
 bool MIME_Entity::GetDataBuffer()
 	{
 	int ret = message->RequestBuffer(&data_buf_length, &data_buf_data);
-	if ( ! ret || data_buf_length == 0 || data_buf_data == 0 )
+	if ( ! ret || data_buf_length == 0 || data_buf_data == nullptr )
 		{
 		// reporter->InternalError("cannot get data buffer from MIME_Message", "");
 		return false;
@@ -1250,18 +1250,18 @@ void MIME_Entity::SubmitAllHeaders()
 
 void MIME_Entity::BeginChildEntity()
 	{
-	ASSERT(current_child_entity == 0);
+	ASSERT(current_child_entity == nullptr);
 	current_child_entity = NewChildEntity();
 	message->BeginEntity(current_child_entity);
 	}
 
 void MIME_Entity::EndChildEntity()
 	{
-	ASSERT(current_child_entity != 0);
+	ASSERT(current_child_entity != nullptr);
 
 	current_child_entity->EndOfData();
 	delete current_child_entity;
-	current_child_entity = 0;
+	current_child_entity = nullptr;
 	}
 
 void MIME_Entity::IllegalFormat(const char* explanation)
@@ -1349,7 +1349,7 @@ MIME_Mail::MIME_Mail(analyzer::Analyzer* mail_analyzer, bool orig, int buf_size)
 
 	content_hash_length = 0;
 
-	top_level = new MIME_Entity(this, 0);	// to be changed to MIME_Mail
+	top_level = new MIME_Entity(this, nullptr);	// to be changed to MIME_Mail
 	BeginEntity(top_level);
 	}
 
diff --git a/src/analyzer/protocol/mime/MIME.h b/src/analyzer/protocol/mime/MIME.h
index f7026bf758..63e8e6b56d 100644
--- a/src/analyzer/protocol/mime/MIME.h
+++ b/src/analyzer/protocol/mime/MIME.h
@@ -188,7 +188,7 @@ public:
 		// Cannot initialize top_level entity because we do
 		// not know its type yet (MIME_Entity / MIME_Mail /
 		// etc.).
-		top_level = 0;
+		top_level = nullptr;
 		finished = false;
 		analyzer = arg_analyzer;
 		}
diff --git a/src/analyzer/protocol/ncp/NCP.cc b/src/analyzer/protocol/ncp/NCP.cc
index 03580d2abb..08ff6d5ac3 100644
--- a/src/analyzer/protocol/ncp/NCP.cc
+++ b/src/analyzer/protocol/ncp/NCP.cc
@@ -83,7 +83,7 @@ void NCP_Session::DeliverFrame(const binpac::NCP::ncp_frame* frame)
 FrameBuffer::FrameBuffer(size_t header_length)
 	{
 	hdr_len = header_length;
-	msg_buf = 0;
+	msg_buf = nullptr;
 	buf_len = 0;
 	Reset();
 	}
diff --git a/src/analyzer/protocol/ncp/Plugin.cc b/src/analyzer/protocol/ncp/Plugin.cc
index 9f17881f1b..b76fcbf748 100644
--- a/src/analyzer/protocol/ncp/Plugin.cc
+++ b/src/analyzer/protocol/ncp/Plugin.cc
@@ -12,7 +12,7 @@ public:
 	plugin::Configuration Configure() override
 		{
 		AddComponent(new ::analyzer::Component("NCP", ::analyzer::ncp::NCP_Analyzer::Instantiate));
-		AddComponent(new ::analyzer::Component("Contents_NCP", 0));
+		AddComponent(new ::analyzer::Component("Contents_NCP", nullptr));
 
 		plugin::Configuration config;
 		config.name = "Zeek::NCP";
diff --git a/src/analyzer/protocol/netbios/NetbiosSSN.cc b/src/analyzer/protocol/netbios/NetbiosSSN.cc
index 31b662d4e6..3af2569738 100644
--- a/src/analyzer/protocol/netbios/NetbiosSSN.cc
+++ b/src/analyzer/protocol/netbios/NetbiosSSN.cc
@@ -214,7 +214,7 @@ int NetbiosSSN_Interpreter::ConvertName(const u_char* name, int name_len,
 	{
 	// Taken from tcpdump's smbutil.c.
 
-	xname = 0;
+	xname = nullptr;
 
 	if ( name_len < 1 )
 		return 0;
@@ -340,7 +340,7 @@ Contents_NetbiosSSN::Contents_NetbiosSSN(Connection* conn, bool orig,
 	{
 	interp = arg_interp;
 	type = flags = msg_size = 0;
-	msg_buf = 0;
+	msg_buf = nullptr;
 	buf_n = buf_len = msg_size = 0;
 	state = NETBIOS_SSN_TYPE;
 	}
@@ -455,7 +455,7 @@ NetbiosSSN_Analyzer::NetbiosSSN_Analyzer(Connection* conn)
 	{
 	//smb_session = new SMB_Session(this);
 	interp = new NetbiosSSN_Interpreter(this);
-	orig_netbios = resp_netbios = 0;
+	orig_netbios = resp_netbios = nullptr;
 	did_session_done = 0;
 
 	if ( Conn()->ConnTransport() == TRANSPORT_TCP )
diff --git a/src/analyzer/protocol/netbios/Plugin.cc b/src/analyzer/protocol/netbios/Plugin.cc
index dde55af51f..47db030464 100644
--- a/src/analyzer/protocol/netbios/Plugin.cc
+++ b/src/analyzer/protocol/netbios/Plugin.cc
@@ -12,7 +12,7 @@ public:
 	plugin::Configuration Configure() override
 		{
 		AddComponent(new ::analyzer::Component("NetbiosSSN", ::analyzer::netbios_ssn::NetbiosSSN_Analyzer::Instantiate));
-		AddComponent(new ::analyzer::Component("Contents_NetbiosSSN", 0));
+		AddComponent(new ::analyzer::Component("Contents_NetbiosSSN", nullptr));
 
 		plugin::Configuration config;
 		config.name = "Zeek::NetBIOS";
diff --git a/src/analyzer/protocol/pia/PIA.cc b/src/analyzer/protocol/pia/PIA.cc
index f57771e708..5845f7d540 100644
--- a/src/analyzer/protocol/pia/PIA.cc
+++ b/src/analyzer/protocol/pia/PIA.cc
@@ -22,7 +22,7 @@ PIA::~PIA()
 
 void PIA::ClearBuffer(Buffer* buffer)
 	{
-	DataBlock* next = 0;
+	DataBlock* next = nullptr;
 	for ( DataBlock* b = buffer->head; b; b = next )
 		{
 		next = b->next;
@@ -31,14 +31,14 @@ void PIA::ClearBuffer(Buffer* buffer)
 		delete b;
 		}
 
-	buffer->head = buffer->tail = 0;
+	buffer->head = buffer->tail = nullptr;
 	buffer->size = 0;
 	}
 
 void PIA::AddToBuffer(Buffer* buffer, uint64_t seq, int len, const u_char* data,
 			bool is_orig, const IP_Hdr* ip)
 	{
-	u_char* tmp = 0;
+	u_char* tmp = nullptr;
 
 	if ( data )
 		{
@@ -47,12 +47,12 @@ void PIA::AddToBuffer(Buffer* buffer, uint64_t seq, int len, const u_char* data,
 		}
 
 	DataBlock* b = new DataBlock;
-	b->ip = ip ? ip->Copy() : 0;
+	b->ip = ip ? ip->Copy() : nullptr;
 	b->data = tmp;
 	b->is_orig = is_orig;
 	b->len = len;
 	b->seq = seq;
-	b->next = 0;
+	b->next = nullptr;
 
 	if ( buffer->tail )
 		{
@@ -117,14 +117,14 @@ void PIA::PIA_DeliverPacket(int len, const u_char* data, bool is_orig, uint64_t
 
 	pkt_buffer.state = new_state;
 
-	current_packet.data = 0;
+	current_packet.data = nullptr;
 	}
 
 void PIA::Match(Rule::PatternType type, const u_char* data, int len,
 		bool is_orig, bool bol, bool eol, bool clear_state)
 	{
 	if ( ! MatcherInitialized(is_orig) )
-		InitEndpointMatcher(AsAnalyzer(), 0, 0, is_orig, this);
+		InitEndpointMatcher(AsAnalyzer(), nullptr, 0, is_orig, this);
 
 	RuleMatcherState::Match(type, data, len, is_orig, bol, eol, clear_state);
 	}
@@ -207,9 +207,9 @@ void PIA_TCP::Init()
 void PIA_TCP::FirstPacket(bool is_orig, const IP_Hdr* ip)
 	{
 	static char dummy_packet[sizeof(struct ip) + sizeof(struct tcphdr)];
-	static struct ip* ip4 = 0;
-	static struct tcphdr* tcp4 = 0;
-	static IP_Hdr* ip4_hdr = 0;
+	static struct ip* ip4 = nullptr;
+	static struct tcphdr* tcp4 = nullptr;
+	static IP_Hdr* ip4_hdr = nullptr;
 
 	DBG_LOG(DBG_ANALYZER, "PIA_TCP[%d] FirstPacket(%s)", GetID(), (is_orig ? "T" : "F"));
 
@@ -277,7 +277,7 @@ void PIA_TCP::DeliverStream(int len, const u_char* data, bool is_orig)
 						SKIPPING : MATCHING_ONLY;
 		}
 
-	DoMatch(data, len, is_orig, false, false, false, 0);
+	DoMatch(data, len, is_orig, false, false, false, nullptr);
 
 	stream_buffer.state = new_state;
 	}
@@ -288,7 +288,7 @@ void PIA_TCP::Undelivered(uint64_t seq, int len, bool is_orig)
 
 	if ( stream_buffer.state == BUFFERING )
 		// We use data=nil to mark an undelivered.
-		AddToBuffer(&stream_buffer, seq, len, 0, is_orig);
+		AddToBuffer(&stream_buffer, seq, len, nullptr, is_orig);
 
 	// No check for buffer overrun here. I think that's ok.
 	}
diff --git a/src/analyzer/protocol/pia/PIA.h b/src/analyzer/protocol/pia/PIA.h
index 467d353464..575cb89571 100644
--- a/src/analyzer/protocol/pia/PIA.h
+++ b/src/analyzer/protocol/pia/PIA.h
@@ -25,7 +25,7 @@ public:
 	// Called when PIA wants to put an Analyzer in charge.  rule is the
 	// signature that triggered the activitation, if any.
 	virtual void ActivateAnalyzer(analyzer::Tag tag,
-					const Rule* rule = 0) = 0;
+					const Rule* rule = nullptr) = 0;
 
 	// Called when PIA wants to remove an Analyzer.
 	virtual void DeactivateAnalyzer(analyzer::Tag tag) = 0;
@@ -58,7 +58,7 @@ protected:
 	};
 
 	struct Buffer {
-		Buffer() { head = tail = 0; size = 0; state = INIT; }
+		Buffer() { head = tail = nullptr; size = 0; state = INIT; }
 
 		DataBlock* head;
 		DataBlock* tail;
@@ -67,15 +67,15 @@ protected:
 	};
 
 	void AddToBuffer(Buffer* buffer, uint64_t seq, int len,
-				const u_char* data, bool is_orig, const IP_Hdr* ip = 0);
+				const u_char* data, bool is_orig, const IP_Hdr* ip = nullptr);
 	void AddToBuffer(Buffer* buffer, int len,
-				const u_char* data, bool is_orig, const IP_Hdr* ip = 0);
+				const u_char* data, bool is_orig, const IP_Hdr* ip = nullptr);
 	void ClearBuffer(Buffer* buffer);
 
 	DataBlock* CurrentPacket()	{ return &current_packet; }
 
 	void DoMatch(const u_char* data, int len, bool is_orig, bool bol,
-			bool eol, bool clear_state, const IP_Hdr* ip = 0);
+			bool eol, bool clear_state, const IP_Hdr* ip = nullptr);
 
 	void SetConn(Connection* c)	{ conn = c; }
 
@@ -161,7 +161,7 @@ protected:
 	void Undelivered(uint64_t seq, int len, bool is_orig) override;
 
 	void ActivateAnalyzer(analyzer::Tag tag,
-					const Rule* rule = 0) override;
+					const Rule* rule = nullptr) override;
 	void DeactivateAnalyzer(analyzer::Tag tag) override;
 
 private:
diff --git a/src/analyzer/protocol/pop3/POP3.cc b/src/analyzer/protocol/pop3/POP3.cc
index c5e2d9bb1f..174d11b826 100644
--- a/src/analyzer/protocol/pop3/POP3.cc
+++ b/src/analyzer/protocol/pop3/POP3.cc
@@ -43,7 +43,7 @@ POP3_Analyzer::POP3_Analyzer(Connection* conn)
 	lastRequiredCommand = 0;
 	authLines = 0;
 
-	mail = 0;
+	mail = nullptr;
 
 	cl_orig = new tcp::ContentLine_Analyzer(conn, true);
 	AddSupportAnalyzer(cl_orig);
@@ -136,7 +136,7 @@ void POP3_Analyzer::ProcessRequest(int length, const char* line)
 		++authLines;
 
 		BroString encoded(line);
-		BroString* decoded = decode_base64(&encoded, 0, Conn());
+		BroString* decoded = decode_base64(&encoded, nullptr, Conn());
 
 		if ( ! decoded )
 			{
@@ -854,7 +854,7 @@ void POP3_Analyzer::EndData()
 		{
 		mail->Done();
 		delete mail;
-		mail = 0;
+		mail = nullptr;
 		}
 	}
 
diff --git a/src/analyzer/protocol/pop3/POP3.h b/src/analyzer/protocol/pop3/POP3.h
index 1af2e4226c..1c92e6005b 100644
--- a/src/analyzer/protocol/pop3/POP3.h
+++ b/src/analyzer/protocol/pop3/POP3.h
@@ -103,7 +103,7 @@ protected:
 	int ParseCmd(string cmd);
 	void AuthSuccessfull();
 	void POP3Event(EventHandlerPtr event, bool is_orig,
-			const char* arg1 = 0, const char* arg2 = 0);
+			const char* arg1 = nullptr, const char* arg2 = nullptr);
 
 	mime::MIME_Mail* mail;
 	list<string> cmds;
diff --git a/src/analyzer/protocol/rdp/RDP.cc b/src/analyzer/protocol/rdp/RDP.cc
index 7deaf6a63f..6b73bcfb1f 100644
--- a/src/analyzer/protocol/rdp/RDP.cc
+++ b/src/analyzer/protocol/rdp/RDP.cc
@@ -12,7 +12,7 @@ RDP_Analyzer::RDP_Analyzer(Connection* c)
 	interp = new binpac::RDP::RDP_Conn(this);
 
 	had_gap = false;
-	pia = 0;
+	pia = nullptr;
 	}
 
 RDP_Analyzer::~RDP_Analyzer()
@@ -66,8 +66,8 @@ void RDP_Analyzer::DeliverStream(int len, const u_char* data, bool orig)
 					return;
 					}
 
-				pia->FirstPacket(true, 0);
-				pia->FirstPacket(false, 0);
+				pia->FirstPacket(true, nullptr);
+				pia->FirstPacket(false, nullptr);
 				}
 
 			ForwardStream(len, data, orig);
diff --git a/src/analyzer/protocol/rpc/MOUNT.cc b/src/analyzer/protocol/rpc/MOUNT.cc
index f15a9f154a..96fb4df1d2 100644
--- a/src/analyzer/protocol/rpc/MOUNT.cc
+++ b/src/analyzer/protocol/rpc/MOUNT.cc
@@ -22,7 +22,7 @@ bool MOUNT_Interp::RPC_BuildCall(RPC_CallInfo* c, const u_char*& buf, int& n)
 
 	uint32_t proc = c->Proc();
 	// The call arguments, depends on the call type obviously ...
-	Val *callarg = 0;
+	Val *callarg = nullptr;
 
 	switch ( proc ) {
 		case BifEnum::MOUNT3::PROC_NULL:
@@ -41,7 +41,7 @@ bool MOUNT_Interp::RPC_BuildCall(RPC_CallInfo* c, const u_char*& buf, int& n)
 		break;
 
 	default:
-		callarg = 0;
+		callarg = nullptr;
 		if ( proc < BifEnum::MOUNT3::PROC_END_OF_PROCS )
 			{
 			// We know the procedure but haven't implemented it.
@@ -65,7 +65,7 @@ bool MOUNT_Interp::RPC_BuildCall(RPC_CallInfo* c, const u_char*& buf, int& n)
 		// RecordVal was allocated but we failed to fill it). So we
 		// Unref() the call arguments, and we are fine.
 		Unref(callarg);
-		callarg = 0;
+		callarg = nullptr;
 		return false;
 		}
 
@@ -78,8 +78,8 @@ bool MOUNT_Interp::RPC_BuildReply(RPC_CallInfo* c, BifEnum::rpc_status rpc_statu
 			       const u_char*& buf, int& n, double start_time,
 			       double last_time, int reply_len)
 	{
-	EventHandlerPtr event = 0;
-	Val* reply = 0;
+	EventHandlerPtr event = nullptr;
+	Val* reply = nullptr;
 	BifEnum::MOUNT3::status_t mount_status = BifEnum::MOUNT3::MNT3_OK;
 	bool rpc_success = ( rpc_status == BifEnum::RPC_SUCCESS );
 
@@ -104,7 +104,7 @@ bool MOUNT_Interp::RPC_BuildReply(RPC_CallInfo* c, BifEnum::rpc_status rpc_statu
 		// We set the buffer to NULL, the function that extract the
 		// reply from the data stream will then return empty records.
 		//
-		buf = NULL;
+		buf = nullptr;
 		n = 0;
 		}
 
@@ -119,14 +119,14 @@ bool MOUNT_Interp::RPC_BuildReply(RPC_CallInfo* c, BifEnum::rpc_status rpc_statu
 		break;
 
 	case BifEnum::MOUNT3::PROC_UMNT:
-		reply = 0;
+		reply = nullptr;
 		n = 0;
 		mount_status = BifEnum::MOUNT3::MNT3_OK;
 		event = mount_proc_umnt;
 		break;
 
 	case BifEnum::MOUNT3::PROC_UMNT_ALL:
-		reply = 0;
+		reply = nullptr;
 		n = 0;
 		mount_status = BifEnum::MOUNT3::MNT3_OK;
 		event = mount_proc_umnt;
@@ -151,7 +151,7 @@ bool MOUNT_Interp::RPC_BuildReply(RPC_CallInfo* c, BifEnum::rpc_status rpc_statu
 		// There was a parse error. We have to unref the reply. (see
 		// also comments in RPC_BuildCall.
 		Unref(reply);
-		reply = 0;
+		reply = nullptr;
 		return false;
 		}
 
@@ -230,7 +230,7 @@ StringVal* MOUNT_Interp::mount3_fh(const u_char*& buf, int& n)
 	const u_char* fh = extract_XDR_opaque(buf, n, fh_n, 64);
 
 	if ( ! fh )
-		return 0;
+		return nullptr;
 
 	return new StringVal(new BroString(fh, fh_n, false));
 	}
@@ -241,7 +241,7 @@ StringVal* MOUNT_Interp::mount3_filename(const u_char*& buf, int& n)
 	const u_char* name = extract_XDR_opaque(buf, n, name_len);
 
 	if ( ! name )
-		return 0;
+		return nullptr;
 
 	return new StringVal(new BroString(name, name_len, false));
 	}
@@ -288,8 +288,8 @@ RecordVal* MOUNT_Interp::mount3_mnt_reply(const u_char*& buf, int& n,
 		}
 	else
 		{
-		rep->Assign(0, 0);
-		rep->Assign(1, 0);
+		rep->Assign(0, nullptr);
+		rep->Assign(1, nullptr);
 		}
 
 	return rep;
@@ -298,7 +298,7 @@ RecordVal* MOUNT_Interp::mount3_mnt_reply(const u_char*& buf, int& n,
 MOUNT_Analyzer::MOUNT_Analyzer(Connection* conn)
 	: RPC_Analyzer("MOUNT", conn, new MOUNT_Interp(this))
 	{
-	orig_rpc = resp_rpc = 0;
+	orig_rpc = resp_rpc = nullptr;
 	}
 
 void MOUNT_Analyzer::Init()
diff --git a/src/analyzer/protocol/rpc/NFS.cc b/src/analyzer/protocol/rpc/NFS.cc
index bb76727705..b709bee680 100644
--- a/src/analyzer/protocol/rpc/NFS.cc
+++ b/src/analyzer/protocol/rpc/NFS.cc
@@ -22,7 +22,7 @@ bool NFS_Interp::RPC_BuildCall(RPC_CallInfo* c, const u_char*& buf, int& n)
 
 	uint32_t proc = c->Proc();
 	// The call arguments, depends on the call type obviously ...
-	Val *callarg = 0;
+	Val *callarg = nullptr;
 
 	switch ( proc ) {
 	case BifEnum::NFS3::PROC_NULL:
@@ -95,7 +95,7 @@ bool NFS_Interp::RPC_BuildCall(RPC_CallInfo* c, const u_char*& buf, int& n)
 		break;
 
 	default:
-		callarg = 0;
+		callarg = nullptr;
 		if ( proc < BifEnum::NFS3::PROC_END_OF_PROCS )
 			{
 			// We know the procedure but haven't implemented it.
@@ -119,7 +119,7 @@ bool NFS_Interp::RPC_BuildCall(RPC_CallInfo* c, const u_char*& buf, int& n)
 		// RecordVal was allocated but we failed to fill it). So we
 		// Unref() the call arguments, and we are fine.
 		Unref(callarg);
-		callarg = 0;
+		callarg = nullptr;
 		return false;
 		}
 
@@ -132,8 +132,8 @@ bool NFS_Interp::RPC_BuildReply(RPC_CallInfo* c, BifEnum::rpc_status rpc_status,
 			       const u_char*& buf, int& n, double start_time,
 			       double last_time, int reply_len)
 	{
-	EventHandlerPtr event = 0;
-	Val *reply = 0;
+	EventHandlerPtr event = nullptr;
+	Val *reply = nullptr;
 	BifEnum::NFS3::status_t nfs_status = BifEnum::NFS3::NFS3ERR_OK;
 	bool rpc_success = ( rpc_status == BifEnum::RPC_SUCCESS );
 
@@ -158,7 +158,7 @@ bool NFS_Interp::RPC_BuildReply(RPC_CallInfo* c, BifEnum::rpc_status rpc_status,
 		// We set the buffer to NULL, the function that extract the
 		// reply from the data stream will then return empty records.
 		//
-		buf = NULL;
+		buf = nullptr;
 		n = 0;
 		}
 
@@ -263,7 +263,7 @@ bool NFS_Interp::RPC_BuildReply(RPC_CallInfo* c, BifEnum::rpc_status rpc_status,
 		// There was a parse error. We have to unref the reply. (see
 		// also comments in RPC_BuildCall.
 		Unref(reply);
-		reply = 0;
+		reply = nullptr;
 		return false;
 		}
 
@@ -303,10 +303,10 @@ StringVal* NFS_Interp::nfs3_file_data(const u_char*& buf, int& n, uint64_t offse
 
 	// check whether we have to deliver data to the event
 	if ( ! BifConst::NFS3::return_data )
-		return 0;
+		return nullptr;
 
 	if ( BifConst::NFS3::return_data_first_only && offset != 0 )
-		return 0;
+		return nullptr;
 
 	// Ok, so we want to return some data
 	data_n = min(data_n, size);
@@ -315,7 +315,7 @@ StringVal* NFS_Interp::nfs3_file_data(const u_char*& buf, int& n, uint64_t offse
 	if ( data && data_n > 0 )
 		return new StringVal(new BroString(data, data_n, false));
 
-	return 0;
+	return nullptr;
 	}
 
 zeek::Args NFS_Interp::event_common_vl(RPC_CallInfo *c, BifEnum::rpc_status rpc_status,
@@ -358,7 +358,7 @@ StringVal* NFS_Interp::nfs3_fh(const u_char*& buf, int& n)
 	const u_char* fh = extract_XDR_opaque(buf, n, fh_n, 64);
 
 	if ( ! fh )
-		return 0;
+		return nullptr;
 
 	return new StringVal(new BroString(fh, fh_n, false));
 	}
@@ -368,22 +368,22 @@ RecordVal* NFS_Interp::nfs3_sattr(const u_char*& buf, int& n)
 	{
 	RecordVal* attrs = new RecordVal(BifType::Record::NFS3::sattr_t);
 
-	attrs->Assign(0, 0); // mode
+	attrs->Assign(0, nullptr); // mode
 	int mode_set_it =  extract_XDR_uint32(buf, n);
 	if ( mode_set_it )
 		attrs->Assign(0, ExtractUint32(buf, n)); // mode
 
-	attrs->Assign(1, 0); // uid
+	attrs->Assign(1, nullptr); // uid
 	int uid_set_it =  extract_XDR_uint32(buf, n);
 	if ( uid_set_it )
 		attrs->Assign(1, ExtractUint32(buf, n)); // uid
 
-	attrs->Assign(2, 0); // gid
+	attrs->Assign(2, nullptr); // gid
 	int gid_set_it =  extract_XDR_uint32(buf, n);
 	if ( gid_set_it )
 		attrs->Assign(2, ExtractUint32(buf, n)); // gid
 
-	attrs->Assign(3, 0); // size
+	attrs->Assign(3, nullptr); // size
 	int size_set_it =  extract_XDR_uint32(buf, n);
 	if ( size_set_it )
 		attrs->Assign(3, ExtractTime(buf, n));	 // size
@@ -406,8 +406,8 @@ RecordVal* NFS_Interp::nfs3_sattr_reply(const u_char*& buf, int& n, BifEnum::NFS
 		}
 	else
 		{
-		rep->Assign(1, 0);
-		rep->Assign(2, 0);
+		rep->Assign(1, nullptr);
+		rep->Assign(2, nullptr);
 		}
 
 	return rep;
@@ -464,7 +464,7 @@ StringVal *NFS_Interp::nfs3_filename(const u_char*& buf, int& n)
 	const u_char* name = extract_XDR_opaque(buf, n, name_len);
 
 	if ( ! name )
-		return 0;
+		return nullptr;
 
 	return new StringVal(new BroString(name, name_len, false));
 	}
@@ -508,7 +508,7 @@ RecordVal* NFS_Interp::nfs3_post_op_attr(const u_char*& buf, int& n)
 	if ( have_attrs )
 		return nfs3_fattr(buf, n);
 
-	return 0;
+	return nullptr;
 	}
 
 StringVal* NFS_Interp::nfs3_post_op_fh(const u_char*& buf, int& n)
@@ -518,7 +518,7 @@ StringVal* NFS_Interp::nfs3_post_op_fh(const u_char*& buf, int& n)
 	if ( have_fh )
 		return nfs3_fh(buf, n);
 
-	return 0;
+	return nullptr;
 	}
 
 RecordVal* NFS_Interp::nfs3_pre_op_attr(const u_char*& buf, int& n)
@@ -527,7 +527,7 @@ RecordVal* NFS_Interp::nfs3_pre_op_attr(const u_char*& buf, int& n)
 
 	if ( have_attrs )
 		return nfs3_wcc_attr(buf, n);
-	return 0;
+	return nullptr;
 	}
 
 EnumVal *NFS_Interp::nfs3_stable_how(const u_char*& buf, int& n)
@@ -548,8 +548,8 @@ RecordVal* NFS_Interp::nfs3_lookup_reply(const u_char*& buf, int& n, BifEnum::NF
 		}
 	else
 		{
-		rep->Assign(0, 0);
-		rep->Assign(1, 0);
+		rep->Assign(0, nullptr);
+		rep->Assign(1, nullptr);
 		rep->Assign(2, nfs3_post_op_attr(buf, n));
 		}
 	return rep;
@@ -710,8 +710,8 @@ RecordVal* NFS_Interp::nfs3_newobj_reply(const u_char*& buf, int& n, BifEnum::NF
 		}
 	else
 		{
-		rep->Assign(0, 0);
-		rep->Assign(1, 0);
+		rep->Assign(0, nullptr);
+		rep->Assign(1, nullptr);
 		rep->Assign(2, nfs3_pre_op_attr(buf, n));
 		rep->Assign(3, nfs3_post_op_attr(buf, n));
 		}
@@ -833,7 +833,7 @@ Val* NFS_Interp::ExtractBool(const u_char*& buf, int& n)
 NFS_Analyzer::NFS_Analyzer(Connection* conn)
 	: RPC_Analyzer("NFS", conn, new NFS_Interp(this))
 	{
-	orig_rpc = resp_rpc = 0;
+	orig_rpc = resp_rpc = nullptr;
 	}
 
 void NFS_Analyzer::Init()
diff --git a/src/analyzer/protocol/rpc/Plugin.cc b/src/analyzer/protocol/rpc/Plugin.cc
index da9b5f0299..6e284c9dbf 100644
--- a/src/analyzer/protocol/rpc/Plugin.cc
+++ b/src/analyzer/protocol/rpc/Plugin.cc
@@ -17,8 +17,8 @@ public:
 		AddComponent(new ::analyzer::Component("NFS", ::analyzer::rpc::NFS_Analyzer::Instantiate));
 		AddComponent(new ::analyzer::Component("MOUNT", ::analyzer::rpc::MOUNT_Analyzer::Instantiate));
 		AddComponent(new ::analyzer::Component("Portmapper", ::analyzer::rpc::Portmapper_Analyzer::Instantiate));
-		AddComponent(new ::analyzer::Component("Contents_RPC", 0));
-		AddComponent(new ::analyzer::Component("Contents_NFS", 0));
+		AddComponent(new ::analyzer::Component("Contents_RPC", nullptr));
+		AddComponent(new ::analyzer::Component("Contents_NFS", nullptr));
 
 		plugin::Configuration config;
 		config.name = "Zeek::RPC";
diff --git a/src/analyzer/protocol/rpc/Portmap.cc b/src/analyzer/protocol/rpc/Portmap.cc
index c67d1b3c52..ad9fa37f02 100644
--- a/src/analyzer/protocol/rpc/Portmap.cc
+++ b/src/analyzer/protocol/rpc/Portmap.cc
@@ -79,7 +79,7 @@ bool PortmapperInterp::RPC_BuildReply(RPC_CallInfo* c, BifEnum::rpc_status statu
 				     int reply_len)
 	{
 	EventHandlerPtr event;
-	Val *reply = 0;
+	Val *reply = nullptr;
 	int success = (status == BifEnum::RPC_SUCCESS);
 
 	switch ( c->Proc() ) {
@@ -208,7 +208,7 @@ Val* PortmapperInterp::ExtractMapping(const u_char*& buf, int& len)
 	if ( ! buf )
 		{
 		Unref(mapping);
-		return 0;
+		return nullptr;
 		}
 
 	return mapping;
@@ -228,7 +228,7 @@ Val* PortmapperInterp::ExtractPortRequest(const u_char*& buf, int& len)
 	if ( ! buf )
 		{
 		Unref(pr);
-		return 0;
+		return nullptr;
 		}
 
 	return pr;
@@ -249,7 +249,7 @@ Val* PortmapperInterp::ExtractCallItRequest(const u_char*& buf, int& len)
 	if ( ! buf )
 		{
 		Unref(c);
-		return 0;
+		return nullptr;
 		}
 
 	return c;
@@ -307,7 +307,7 @@ void PortmapperInterp::Event(EventHandlerPtr f, Val* request, BifEnum::rpc_statu
 Portmapper_Analyzer::Portmapper_Analyzer(Connection* conn)
 : RPC_Analyzer("PORTMAPPER", conn, new PortmapperInterp(this))
 	{
-	orig_rpc = resp_rpc = 0;
+	orig_rpc = resp_rpc = nullptr;
 	}
 
 Portmapper_Analyzer::~Portmapper_Analyzer()
diff --git a/src/analyzer/protocol/rpc/RPC.h b/src/analyzer/protocol/rpc/RPC.h
index 60488cd6d0..2aa8f14d31 100644
--- a/src/analyzer/protocol/rpc/RPC.h
+++ b/src/analyzer/protocol/rpc/RPC.h
@@ -54,7 +54,7 @@ public:
 
 	void AddVal(Val* arg_v)		{ Unref(v); v = arg_v; }
 	Val* RequestVal() const		{ return v; }
-	Val* TakeRequestVal()		{ Val* rv = v; v = 0; return rv; }
+	Val* TakeRequestVal()		{ Val* rv = v; v = nullptr; return rv; }
 
 	bool CompareRexmit(const u_char* buf, int n) const;
 
@@ -149,7 +149,7 @@ public:
 	RPC_Reasm_Buffer() {
 		maxsize = expected = 0;
 		fill = processed = 0;
-		buf = 0;
+		buf = nullptr;
 	};
 
 	~RPC_Reasm_Buffer() { if (buf) delete [] buf; }
diff --git a/src/analyzer/protocol/rpc/XDR.cc b/src/analyzer/protocol/rpc/XDR.cc
index 95992d142c..1eddf96a04 100644
--- a/src/analyzer/protocol/rpc/XDR.cc
+++ b/src/analyzer/protocol/rpc/XDR.cc
@@ -17,7 +17,7 @@ uint32_t analyzer::rpc::extract_XDR_uint32(const u_char*& buf, int& len)
 
 	if ( len < 4 )
 		{
-		buf = 0;
+		buf = nullptr;
 		return 0;
 		}
 
@@ -36,7 +36,7 @@ uint64_t analyzer::rpc::extract_XDR_uint64(const u_char*& buf, int& len)
 	{
 	if ( ! buf || len < 8 )
 		{
-		buf = 0;
+		buf = nullptr;
 		return 0;
 		}
 
@@ -50,7 +50,7 @@ double analyzer::rpc::extract_XDR_time(const u_char*& buf, int& len)
 	{
 	if ( ! buf || len < 8 )
 		{
-		buf = 0;
+		buf = nullptr;
 		return 0.0;
 		}
 
@@ -64,15 +64,15 @@ const u_char* analyzer::rpc::extract_XDR_opaque(const u_char*& buf, int& len, in
 	{
 	n = int(extract_XDR_uint32(buf, len));
 	if ( ! buf )
-		return 0;
+		return nullptr;
 
 	if ( short_buf_ok )
 		n = std::min(n, len);
 
 	if ( n < 0 || n > len || n > max_len )
 		{ // ### Should really flag this as a different sort of error.
-		buf = 0;
-		return 0;
+		buf = nullptr;
+		return nullptr;
 		}
 
 	int n4 = ((n + 3) >> 2) << 2;	// n rounded up to next multiple of 4
@@ -87,11 +87,11 @@ const u_char* analyzer::rpc::extract_XDR_opaque(const u_char*& buf, int& len, in
 const u_char* analyzer::rpc::extract_XDR_opaque_fixed(const u_char*& buf, int& len, int n)
 	{
 	if ( ! buf )
-		return 0;
+		return nullptr;
 	if ( n < 0 || n > len)
 		{
-		buf = 0;
-		return 0;
+		buf = nullptr;
+		return nullptr;
 		}
 	int n4 = ((n + 3) >> 2) << 2;	// n rounded up to next multiple of 4
 
diff --git a/src/analyzer/protocol/smb/Plugin.cc b/src/analyzer/protocol/smb/Plugin.cc
index aaf84af9f5..2c10066eed 100644
--- a/src/analyzer/protocol/smb/Plugin.cc
+++ b/src/analyzer/protocol/smb/Plugin.cc
@@ -12,7 +12,7 @@ public:
 	plugin::Configuration Configure() override
 		{
 		AddComponent(new ::analyzer::Component("SMB", ::analyzer::smb::SMB_Analyzer::Instantiate));
-		AddComponent(new ::analyzer::Component("Contents_SMB", 0));
+		AddComponent(new ::analyzer::Component("Contents_SMB", nullptr));
 
 		plugin::Configuration config;
 		config.name = "Zeek::SMB";
diff --git a/src/analyzer/protocol/smtp/SMTP.cc b/src/analyzer/protocol/smtp/SMTP.cc
index eee9ac81b8..0494bee0c0 100644
--- a/src/analyzer/protocol/smtp/SMTP.cc
+++ b/src/analyzer/protocol/smtp/SMTP.cc
@@ -43,8 +43,8 @@ SMTP_Analyzer::SMTP_Analyzer(Connection* conn)
 
 	skip_data = false;
 	orig_is_sender = true;
-	line_after_gap = 0;
-	mail = 0;
+	line_after_gap = nullptr;
+	mail = nullptr;
 	UpdateState(first_cmd, 0, true);
 	cl_orig = new tcp::ContentLine_Analyzer(conn, true);
 	cl_orig->SetIsNULSensitive(true);
@@ -103,7 +103,7 @@ void SMTP_Analyzer::Undelivered(uint64_t seq, int len, bool is_orig)
 	if ( line_after_gap )
 		{
 		delete line_after_gap;
-		line_after_gap = 0;
+		line_after_gap = nullptr;
 		}
 
 	pending_cmd_q.clear();
@@ -247,7 +247,7 @@ void SMTP_Analyzer::ProcessLine(int length, const char* line, bool orig)
 			if ( cmd_code == -1 )
 				{
 				Unexpected(true, "unknown command", cmd_len, cmd);
-				cmd = 0;
+				cmd = nullptr;
 				}
 			else
 				NewCmd(cmd_code);
@@ -921,7 +921,7 @@ void SMTP_Analyzer::BeginData(bool orig)
 	{
 	state = SMTP_IN_DATA;
 	skip_data = false; // reset the flag at the beginning of the mail
-	if ( mail != 0 )
+	if ( mail != nullptr )
 		{
 		Weird("smtp_nested_mail_transaction");
 		mail->Done();
@@ -939,6 +939,6 @@ void SMTP_Analyzer::EndData()
 		{
 		mail->Done();
 		delete mail;
-		mail = 0;
+		mail = nullptr;
 		}
 	}
diff --git a/src/analyzer/protocol/socks/SOCKS.cc b/src/analyzer/protocol/socks/SOCKS.cc
index 83663f41b6..6490f38165 100644
--- a/src/analyzer/protocol/socks/SOCKS.cc
+++ b/src/analyzer/protocol/socks/SOCKS.cc
@@ -11,7 +11,7 @@ SOCKS_Analyzer::SOCKS_Analyzer(Connection* conn)
 	{
 	interp = new binpac::SOCKS::SOCKS_Conn(this);
 	orig_done = resp_done = false;
-	pia = 0;
+	pia = nullptr;
 	}
 
 SOCKS_Analyzer::~SOCKS_Analyzer()
@@ -63,11 +63,11 @@ void SOCKS_Analyzer::DeliverStream(int len, const u_char* data, bool orig)
 			pia = new pia::PIA_TCP(Conn());
 			if ( AddChildAnalyzer(pia) )
 				{
-				pia->FirstPacket(true, 0);
-				pia->FirstPacket(false, 0);
+				pia->FirstPacket(true, nullptr);
+				pia->FirstPacket(false, nullptr);
 				}
 			else
-				pia = 0;
+				pia = nullptr;
 			}
 
 		ForwardStream(len, data, orig);
diff --git a/src/analyzer/protocol/stepping-stone/SteppingStone.cc b/src/analyzer/protocol/stepping-stone/SteppingStone.cc
index 54351768f4..42332a59c5 100644
--- a/src/analyzer/protocol/stepping-stone/SteppingStone.cc
+++ b/src/analyzer/protocol/stepping-stone/SteppingStone.cc
@@ -158,7 +158,7 @@ SteppingStone_Analyzer::SteppingStone_Analyzer(Connection* c)
 	{
 	stp_manager = sessions->GetSTPManager();
 
-	orig_endp = resp_endp = 0;
+	orig_endp = resp_endp = nullptr;
 	orig_stream_pos = resp_stream_pos = 1;
 	}
 
@@ -179,9 +179,9 @@ void SteppingStone_Analyzer::DeliverPacket(int len, const u_char* data,
 						ip, caplen);
 
 	if ( is_orig )
-		orig_endp->DataSent(network_time, seq, len, caplen, data, 0, 0);
+		orig_endp->DataSent(network_time, seq, len, caplen, data, nullptr, nullptr);
 	else
-		resp_endp->DataSent(network_time, seq, len, caplen, data, 0, 0);
+		resp_endp->DataSent(network_time, seq, len, caplen, data, nullptr, nullptr);
 	}
 
 void SteppingStone_Analyzer::DeliverStream(int len, const u_char* data,
@@ -192,14 +192,14 @@ void SteppingStone_Analyzer::DeliverStream(int len, const u_char* data,
 	if ( is_orig )
 		{
 		orig_endp->DataSent(network_time, orig_stream_pos, len, len,
-					data, 0, 0);
+					data, nullptr, nullptr);
 		orig_stream_pos += len;
 		}
 
 	else
 		{
 		resp_endp->DataSent(network_time, resp_stream_pos, len, len,
-					data, 0, 0);
+					data, nullptr, nullptr);
 		resp_stream_pos += len;
 		}
 	}
diff --git a/src/analyzer/protocol/tcp/ContentLine.cc b/src/analyzer/protocol/tcp/ContentLine.cc
index 193a18fa65..5e0dfd81b2 100644
--- a/src/analyzer/protocol/tcp/ContentLine.cc
+++ b/src/analyzer/protocol/tcp/ContentLine.cc
@@ -24,7 +24,7 @@ void ContentLine_Analyzer::InitState()
 	CR_LF_as_EOL = (CR_as_EOL | LF_as_EOL);
 	skip_deliveries = false;
 	skip_partial = false;
-	buf = 0;
+	buf = nullptr;
 	seq_delivered_in_lines = 0;
 	skip_pending = 0;
 	seq = 0;
diff --git a/src/analyzer/protocol/tcp/Plugin.cc b/src/analyzer/protocol/tcp/Plugin.cc
index d96c3ca3ed..9f06936baa 100644
--- a/src/analyzer/protocol/tcp/Plugin.cc
+++ b/src/analyzer/protocol/tcp/Plugin.cc
@@ -13,8 +13,8 @@ public:
 		{
 		AddComponent(new ::analyzer::Component("TCP", ::analyzer::tcp::TCP_Analyzer::Instantiate));
 		AddComponent(new ::analyzer::Component("TCPStats", ::analyzer::tcp::TCPStats_Analyzer::Instantiate));
-		AddComponent(new ::analyzer::Component("CONTENTLINE", 0));
-		AddComponent(new ::analyzer::Component("Contents", 0));
+		AddComponent(new ::analyzer::Component("CONTENTLINE", nullptr));
+		AddComponent(new ::analyzer::Component("Contents", nullptr));
 
 		plugin::Configuration config;
 		config.name = "Zeek::TCP";
diff --git a/src/analyzer/protocol/tcp/TCP.cc b/src/analyzer/protocol/tcp/TCP.cc
index 6d6ad3a41b..8a8f300397 100644
--- a/src/analyzer/protocol/tcp/TCP.cc
+++ b/src/analyzer/protocol/tcp/TCP.cc
@@ -192,7 +192,7 @@ analyzer::Analyzer* TCP_Analyzer::FindChild(ID arg_id)
 			return child;
 		}
 
-	return 0;
+	return nullptr;
 	}
 
 analyzer::Analyzer* TCP_Analyzer::FindChild(Tag arg_tag)
@@ -209,7 +209,7 @@ analyzer::Analyzer* TCP_Analyzer::FindChild(Tag arg_tag)
 			return child;
 		}
 
-	return 0;
+	return nullptr;
 	}
 
 bool TCP_Analyzer::RemoveChildAnalyzer(ID id)
@@ -253,7 +253,7 @@ const struct tcphdr* TCP_Analyzer::ExtractTCP_Header(const u_char*& data,
 	if ( tcp_hdr_len < sizeof(struct tcphdr) )
 		{
 		Weird("bad_TCP_header_len");
-		return 0;
+		return nullptr;
 		}
 
 	if ( tcp_hdr_len > uint32_t(len) ||
@@ -262,7 +262,7 @@ const struct tcphdr* TCP_Analyzer::ExtractTCP_Header(const u_char*& data,
 		// This can happen even with the above test, due to TCP
 		// options.
 		Weird("truncated_header");
-		return 0;
+		return nullptr;
 		}
 
 	len -= tcp_hdr_len;	// remove TCP header
@@ -1587,8 +1587,8 @@ void TCP_Analyzer::SetContentsFile(unsigned int direction, BroFile* f)
 	{
 	if ( direction == CONTENTS_NONE )
 		{
-		orig->SetContentsFile(0);
-		resp->SetContentsFile(0);
+		orig->SetContentsFile(nullptr);
+		resp->SetContentsFile(nullptr);
 		}
 
 	else
@@ -1604,7 +1604,7 @@ BroFile* TCP_Analyzer::GetContentsFile(unsigned int direction) const
 	{
 	switch ( direction ) {
 	case CONTENTS_NONE:
-		return 0;
+		return nullptr;
 
 	case CONTENTS_ORIG:
 		return orig->GetContentsFile();
@@ -1615,7 +1615,7 @@ BroFile* TCP_Analyzer::GetContentsFile(unsigned int direction) const
 	case CONTENTS_BOTH:
 		if ( orig->GetContentsFile() != resp->GetContentsFile())
 			// This is an "error".
-			return 0;
+			return nullptr;
 		else
 			return orig->GetContentsFile();
 
@@ -1625,7 +1625,7 @@ BroFile* TCP_Analyzer::GetContentsFile(unsigned int direction) const
 
 	reporter->Error("bad direction %u in TCP_Analyzer::GetContentsFile",
 	                direction);
-	return 0;
+	return nullptr;
 	}
 
 void TCP_Analyzer::ConnectionClosed(TCP_Endpoint* endpoint, TCP_Endpoint* peer,
@@ -2127,7 +2127,7 @@ void TCPStats_Analyzer::DeliverPacket(int len, const u_char* data, bool is_orig,
 	TCP_ApplicationAnalyzer::DeliverPacket(len, data, is_orig, seq, ip, caplen);
 
 	if ( is_orig )
-		orig_stats->DataSent(network_time, seq, len, caplen, data, ip, 0);
+		orig_stats->DataSent(network_time, seq, len, caplen, data, ip, nullptr);
 	else
-		resp_stats->DataSent(network_time, seq, len, caplen, data, ip, 0);
+		resp_stats->DataSent(network_time, seq, len, caplen, data, ip, nullptr);
 	}
diff --git a/src/analyzer/protocol/tcp/TCP.h b/src/analyzer/protocol/tcp/TCP.h
index 1a2d29c8b2..5e7781f62f 100644
--- a/src/analyzer/protocol/tcp/TCP.h
+++ b/src/analyzer/protocol/tcp/TCP.h
@@ -161,7 +161,7 @@ protected:
 	// A couple utility functions that may also be useful to derived analyzers.
 	static uint64_t get_relative_seq(const TCP_Endpoint* endpoint,
 	                               uint32_t cur_base, uint32_t last,
-	                               uint32_t wraps, bool* underflow = 0);
+	                               uint32_t wraps, bool* underflow = nullptr);
 
 	static int get_segment_len(int payload_len, TCP_Flags flags);
 
@@ -192,12 +192,10 @@ private:
 class TCP_ApplicationAnalyzer : public analyzer::Analyzer {
 public:
 	TCP_ApplicationAnalyzer(const char* name, Connection* conn)
-	: Analyzer(name, conn)
-		{ tcp = 0; }
+		: Analyzer(name, conn), tcp(nullptr) { }
 
 	explicit TCP_ApplicationAnalyzer(Connection* conn)
-	: Analyzer(conn)
-		{ tcp = 0; }
+		: Analyzer(conn), tcp(nullptr) { }
 
 	~TCP_ApplicationAnalyzer() override { }
 
@@ -235,7 +233,7 @@ public:
 	// This suppresses violations if the TCP connection wasn't
 	// fully established.
 	void ProtocolViolation(const char* reason,
-					const char* data = 0, int len = 0) override;
+					const char* data = nullptr, int len = 0) override;
 
 	// "name" and "val" both now belong to this object, which needs to
 	//  delete them when done with them.
diff --git a/src/analyzer/protocol/tcp/TCP_Endpoint.cc b/src/analyzer/protocol/tcp/TCP_Endpoint.cc
index 59f0b21778..f0fb129d6d 100644
--- a/src/analyzer/protocol/tcp/TCP_Endpoint.cc
+++ b/src/analyzer/protocol/tcp/TCP_Endpoint.cc
@@ -16,9 +16,9 @@ using namespace analyzer::tcp;
 
 TCP_Endpoint::TCP_Endpoint(TCP_Analyzer* arg_analyzer, bool arg_is_orig)
 	{
-	contents_processor = 0;
+	contents_processor = nullptr;
 	prev_state = state = TCP_ENDPOINT_INACTIVE;
-	peer = 0;
+	peer = nullptr;
 	start_time = last_time = 0.0;
 	start_seq = last_seq = ack_seq = 0;
 	seq_wraps = ack_wraps = 0;
@@ -29,7 +29,7 @@ TCP_Endpoint::TCP_Endpoint(TCP_Analyzer* arg_analyzer, bool arg_is_orig)
 	FIN_seq = 0;
 	SYN_cnt = FIN_cnt = RST_cnt = 0;
 	did_close = false;
-	contents_file = 0;
+	contents_file = nullptr;
 	tcp_analyzer = arg_analyzer;
 	is_orig = arg_is_orig;
 
diff --git a/src/analyzer/protocol/tcp/TCP_Endpoint.h b/src/analyzer/protocol/tcp/TCP_Endpoint.h
index 79c9ee2849..e72016e4a2 100644
--- a/src/analyzer/protocol/tcp/TCP_Endpoint.h
+++ b/src/analyzer/protocol/tcp/TCP_Endpoint.h
@@ -141,7 +141,7 @@ public:
 
 	Connection* Conn() const;
 
-	bool HasContents() const		{ return contents_processor != 0; }
+	bool HasContents() const		{ return contents_processor != nullptr; }
 	bool HadGap() const;
 
 	inline bool IsOrig() const		{ return is_orig; }
diff --git a/src/analyzer/protocol/tcp/TCP_Reassembler.cc b/src/analyzer/protocol/tcp/TCP_Reassembler.cc
index f77cbda026..697e8d7325 100644
--- a/src/analyzer/protocol/tcp/TCP_Reassembler.cc
+++ b/src/analyzer/protocol/tcp/TCP_Reassembler.cc
@@ -30,7 +30,7 @@ TCP_Reassembler::TCP_Reassembler(analyzer::Analyzer* arg_dst_analyzer,
 	type = arg_type;
 	endp = arg_endp;
 	had_gap = false;
-	record_contents_file = 0;
+	record_contents_file = nullptr;
 	deliver_tcp_contents = false;
 	skip_deliveries = false;
 	did_EOF = false;
diff --git a/src/analyzer/protocol/tcp/functions.bif b/src/analyzer/protocol/tcp/functions.bif
index 5c6448eec1..7b0e2b6876 100644
--- a/src/analyzer/protocol/tcp/functions.bif
+++ b/src/analyzer/protocol/tcp/functions.bif
@@ -121,7 +121,7 @@ function set_contents_file%(cid: conn_id, direction: count, f: file%): bool
 function get_contents_file%(cid: conn_id, direction: count%): file
 	%{
 	Connection* c = sessions->FindConnection(cid);
-	BroFile* f = c ? c->GetRootAnalyzer()->GetContentsFile(direction) : 0;
+	BroFile* f = c ? c->GetRootAnalyzer()->GetContentsFile(direction) : nullptr;
 
 	if ( f )
 		{
diff --git a/src/analyzer/protocol/teredo/Teredo.cc b/src/analyzer/protocol/teredo/Teredo.cc
index 2089fd3f3e..3b1667be29 100644
--- a/src/analyzer/protocol/teredo/Teredo.cc
+++ b/src/analyzer/protocol/teredo/Teredo.cc
@@ -98,9 +98,9 @@ bool TeredoEncapsulation::DoParse(const u_char* data, int& len,
 
 RecordVal* TeredoEncapsulation::BuildVal(const IP_Hdr* inner) const
 	{
-	static RecordType* teredo_hdr_type = 0;
-	static RecordType* teredo_auth_type = 0;
-	static RecordType* teredo_origin_type = 0;
+	static RecordType* teredo_hdr_type = nullptr;
+	static RecordType* teredo_auth_type = nullptr;
+	static RecordType* teredo_origin_type = nullptr;
 
 	if ( ! teredo_hdr_type )
 		{
@@ -167,7 +167,7 @@ void Teredo_Analyzer::DeliverPacket(int len, const u_char* data, bool orig,
 		return;
 		}
 
-	IP_Hdr* inner = 0;
+	IP_Hdr* inner = nullptr;
 	int rslt = sessions->ParseIPPacket(len, te.InnerIP(), IPPROTO_IPV6, inner);
 
 	if ( rslt > 0 )
@@ -201,33 +201,33 @@ void Teredo_Analyzer::DeliverPacket(int len, const u_char* data, bool orig,
 		return;
 		}
 
-	Val* teredo_hdr = 0;
+	Val* teredo_hdr = nullptr;
 
 	if ( teredo_packet )
 		{
 		teredo_hdr = te.BuildVal(inner);
-		Conn()->Event(teredo_packet, 0, teredo_hdr);
+		Conn()->Event(teredo_packet, nullptr, teredo_hdr);
 		}
 
 	if ( te.Authentication() && teredo_authentication )
 		{
 		teredo_hdr = teredo_hdr ? teredo_hdr->Ref() : te.BuildVal(inner);
-		Conn()->Event(teredo_authentication, 0, teredo_hdr);
+		Conn()->Event(teredo_authentication, nullptr, teredo_hdr);
 		}
 
 	if ( te.OriginIndication() && teredo_origin_indication )
 		{
 		teredo_hdr = teredo_hdr ? teredo_hdr->Ref() : te.BuildVal(inner);
-		Conn()->Event(teredo_origin_indication, 0, teredo_hdr);
+		Conn()->Event(teredo_origin_indication, nullptr, teredo_hdr);
 		}
 
 	if ( inner->NextProto() == IPPROTO_NONE && teredo_bubble )
 		{
 		teredo_hdr = teredo_hdr ? teredo_hdr->Ref() : te.BuildVal(inner);
-		Conn()->Event(teredo_bubble, 0, teredo_hdr);
+		Conn()->Event(teredo_bubble, nullptr, teredo_hdr);
 		}
 
 	EncapsulatingConn ec(Conn(), BifEnum::Tunnel::TEREDO);
 
-	sessions->DoNextInnerPacket(network_time, 0, inner, e, ec);
+	sessions->DoNextInnerPacket(network_time, nullptr, inner, e, ec);
 	}
diff --git a/src/analyzer/protocol/teredo/Teredo.h b/src/analyzer/protocol/teredo/Teredo.h
index e76b6b7ba8..3d0fd00ffe 100644
--- a/src/analyzer/protocol/teredo/Teredo.h
+++ b/src/analyzer/protocol/teredo/Teredo.h
@@ -55,7 +55,7 @@ protected:
 class TeredoEncapsulation {
 public:
 	explicit TeredoEncapsulation(const Teredo_Analyzer* ta)
-		: inner_ip(0), origin_indication(0), auth(0), analyzer(ta)
+		: inner_ip(nullptr), origin_indication(nullptr), auth(nullptr), analyzer(ta)
 		{}
 
 	/**
diff --git a/src/analyzer/protocol/vxlan/VXLAN.cc b/src/analyzer/protocol/vxlan/VXLAN.cc
index b7ed5322f7..ff41444295 100644
--- a/src/analyzer/protocol/vxlan/VXLAN.cc
+++ b/src/analyzer/protocol/vxlan/VXLAN.cc
@@ -101,7 +101,7 @@ void VXLAN_Analyzer::DeliverPacket(int len, const u_char* data, bool orig,
 	ProtocolConfirmation();
 
 	if ( vxlan_packet )
-		Conn()->Event(vxlan_packet, 0, inner->BuildPktHdrVal(),
+		Conn()->Event(vxlan_packet, nullptr, inner->BuildPktHdrVal(),
 		              val_mgr->GetCount(vni));
 
 	EncapsulatingConn ec(Conn(), BifEnum::Tunnel::VXLAN);
diff --git a/src/analyzer/protocol/zip/Plugin.cc b/src/analyzer/protocol/zip/Plugin.cc
index e80d4c6a8c..d59cde2ca0 100644
--- a/src/analyzer/protocol/zip/Plugin.cc
+++ b/src/analyzer/protocol/zip/Plugin.cc
@@ -11,7 +11,7 @@ class Plugin : public plugin::Plugin {
 public:
 	plugin::Configuration Configure() override
 		{
-		AddComponent(new ::analyzer::Component("ZIP", 0));
+		AddComponent(new ::analyzer::Component("ZIP", nullptr));
 
 		plugin::Configuration config;
 		config.name = "Zeek::ZIP";
diff --git a/src/analyzer/protocol/zip/ZIP.cc b/src/analyzer/protocol/zip/ZIP.cc
index d44c6353cd..4b94912e75 100644
--- a/src/analyzer/protocol/zip/ZIP.cc
+++ b/src/analyzer/protocol/zip/ZIP.cc
@@ -7,7 +7,7 @@ using namespace analyzer::zip;
 ZIP_Analyzer::ZIP_Analyzer(Connection* conn, bool orig, Method arg_method)
 : tcp::TCP_SupportAnalyzer("ZIP", conn, orig)
 	{
-	zip = 0;
+	zip = nullptr;
 	zip_status = Z_OK;
 	method = arg_method;
 
@@ -26,7 +26,7 @@ ZIP_Analyzer::ZIP_Analyzer(Connection* conn, bool orig, Method arg_method)
 		{
 		Weird("inflate_init_failed");
 		delete zip;
-		zip = 0;
+		zip = nullptr;
 		}
 	}