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60 lines
2.2 KiB
Text
60 lines
2.2 KiB
Text
##! FTP brute-forcing detector, triggering when too many rejected usernames or
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##! failed passwords have occurred from a single address.
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@load base/protocols/ftp
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@load base/frameworks/sumstats
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@load base/utils/time
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module FTP;
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export {
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redef enum Notice::Type += {
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## Indicates a host bruteforcing FTP logins by watching for too
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## many rejected usernames or failed passwords.
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Bruteforcing
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};
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## How many rejected usernames or passwords are required before being
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## considered to be bruteforcing.
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const bruteforce_threshold: double = 20 &redef;
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## The time period in which the threshold needs to be crossed before
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## being reset.
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const bruteforce_measurement_interval = 15mins &redef;
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}
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event bro_init()
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{
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local r1: SumStats::Reducer = [$stream="ftp.failed_auth", $apply=set(SumStats::UNIQUE), $unique_max=double_to_count(bruteforce_threshold+2)];
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SumStats::create([$name="ftp-detect-bruteforcing",
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$epoch=bruteforce_measurement_interval,
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$reducers=set(r1),
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$threshold_val(key: SumStats::Key, result: SumStats::Result) =
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{
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return result["ftp.failed_auth"]$num+0.0;
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},
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$threshold=bruteforce_threshold,
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$threshold_crossed(key: SumStats::Key, result: SumStats::Result) =
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{
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local r = result["ftp.failed_auth"];
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local dur = duration_to_mins_secs(r$end-r$begin);
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local plural = r$unique>1 ? "s" : "";
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local message = fmt("%s had %d failed logins on %d FTP server%s in %s", key$host, r$num, r$unique, plural, dur);
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NOTICE([$note=FTP::Bruteforcing,
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$src=key$host,
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$msg=message,
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$identifier=cat(key$host)]);
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}]);
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}
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event ftp_reply(c: connection, code: count, msg: string, cont_resp: bool)
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{
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local cmd = c$ftp$cmdarg$cmd;
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if ( cmd == "USER" || cmd == "PASS" )
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{
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if ( FTP::parse_ftp_reply_code(code)$x == 5 )
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SumStats::observe("ftp.failed_auth", [$host=c$id$orig_h], [$str=cat(c$id$resp_h)]);
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}
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}
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