zeek/scripts/policy/protocols/ftp/detect-bruteforcing.zeek
Benjamin Bannier d5fd29edcd Prefer explicit construction to coercion in record initialization
While we support initializing records via coercion from an expression
list, e.g.,

    local x: X = [$x1=1, $x2=2];

this can sometimes obscure the code to readers, e.g., when assigning to
value declared and typed elsewhere. The language runtime has a similar
overhead since instead of just constructing a known type it needs to
check at runtime that the coercion from the expression list is valid;
this can be slower than just writing the readible code in the first
place, see #4559.

With this patch we use explicit construction, e.g.,

    local x = X($x1=1, $x2=2);
2025-07-11 16:28:37 -07:00

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