[Snort-sigs] Local.Rules rule misfiring
Rodgers, Anthony (DTMB)
RodgersA1 at ...3985...
Fri Apr 29 08:21:04 EDT 2016
As I read your rule, it will match on $EXTERNAL_NET - IP address matching is not first-match, AFAIK.
If you want to exclude (a) specific address(es) from causing a rule to fire, you should look at event suppression or detection_filter, not negation.
Michigan Security Operations Center (MiSOC)
DTMB, Michigan Cyber Security
From: Clint Conner [mailto:conner at ...4151...]
Sent: Tuesday, April 26, 2016 10:06
To: snort-sigs at lists.sourceforge.net
Subject: [Snort-sigs] Local.Rules rule misfiring
I have the following rule added to my local.rules file. The rule it replaces is disabled in disabledsids.conf. The rule is firing incorrectly, though. It alerts on the first IP address, which is 126.96.36.199. If I understand he rule correctly, it should not be alerting on this IP address.
alert tcp $HOME_NET any -> [!188.8.131.52,!184.108.40.206/21,$EXTERNAL_NET] $HTTP_PORTS (msg:"ET MALWARE User-Agent (Mozilla/4.0 (compatible))";flow:to_server,established; content:"User-Agent|3a| Mozilla/4.0 (compatible|29 0d 0a|"; fast_pattern:18,20; http_header; content:!"citrixonline.com"; http_header; reference:url,doc.emergingthreats.net/bin/view/Main/2008974; classtype:Trojan-activity; sid:900000010;rev:1;)
There are more IP address ranges that are ! out, but I have omitted them. I copied the rule directly from the pulledpork file and just added the first IP address to it. I still have alerts pouring in when anything goes to that first IP address.
Clint J. Conner
Managed Services Manager
Plummer Slade, Inc.
"Computer Networking & IT Solutions"
428 Forbes Avenue, Suite 2450<x-apple-data-detectors://3/0>
Pittsburgh, PA 15219<x-apple-data-detectors://3/0>
Tel: 412.261.5600 x215<tel:412.261.5600;215>
conner at ...4151...<mailto:conner at ...4151...>
"Exclusively endorsed for IT solutions by the Allegheny County Bar Association (ACBA)."
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