zeek/scripts/policy/protocols/ftp/detect-bruteforcing.bro
2013-03-13 22:55:03 -04:00

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@load base/protocols/ftp
@load base/frameworks/measurement
@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 = 20 &redef;
## The time period in which the threshold needs to be crossed before
## being reset.
const bruteforce_measurement_interval = 15mins &redef;
}
event bro_init()
{
Metrics::add_filter("ftp.failed_auth", [$every=bruteforce_measurement_interval,
$measure=set(Metrics::UNIQUE),
$threshold_val_func(val: Metrics::ResultVal) = { return val$num; },
$threshold=bruteforce_threshold,
$threshold_crossed(index: Metrics::Index, val: Metrics::ResultVal) =
{
local dur = duration_to_mins_secs(val$end-val$begin);
local plural = val$unique>1 ? "s" : "";
local message = fmt("%s had %d failed logins on %d FTP server%s in %s", index$host, val$num, val$unique, plural, dur);
NOTICE([$note=FTP::Bruteforcing,
$src=index$host,
$msg=message,
$identifier=cat(index$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 )
Metrics::add_data("ftp.failed_auth", [$host=c$id$orig_h], [$str=cat(c$id$resp_h)]);
}
}