[Snort-users] Mcafee IDS rule processing

Joel Esler (jesler) jesler at ...589...
Tue Feb 16 23:01:24 EST 2016

Unfortunately, we have no idea how the mcafee engine is parsing our rules, and obviously is not parsing them correctly.  As the pcre clearly defines that this alert shouldn't have taken place.

Joel Esler

On Feb 16, 2016, at 10:50 PM, Adrian Good <itsa.aacgood at ...11827...<mailto:itsa.aacgood at ...11827...>> wrote:

Hi all,

I am attempting to troubleshoot a particular snort rule that has been added to a custom attack set on our Mcafee IDS, and I am hoping that someone can point me in the right direction.

The rule is below (sid:31229):
alert tcp any any -> any [36,80,81,82,83,84,85,86,87,88,89,90,311,383,555,591,593,631,801,808,818,901,972,1158,1220,1414,1533,1741,1830,1942,2231,2301,2381,2578,2809,2980,3029,3037,3057,3128,3443,3702,4000,4343,4848,5000,5117,5250,5600,6080,6173,6988,7000,7001,7071,7144,7145,7510,7770,7777,7778,7779,8000,8008,8014,8028,8080,8081,8082,8085,8088,8090,8118,8123,8180,8181,8222,8243,8280,8300,8333,8344,8500,8509,8800,8888,8899,8983,9000,9060,9080,9090,9091,9111,9290,9443,9999,10000,11371,12601,13014,15489,29991,33300,34412,34443,34444,41080,44449,50000,50002,51423,53331,55252,55555,56712] (msg:"EXPLOIT-KIT Bleeding Life exploit kit outbound Adobe Flash exploit request"; flow:to_server,established; content:"/modules/"; fast_pattern:only; http_uri; pcre:"/\/modules\/(n?\d|nu)\.swf$/U"; metadata:policy balanced-ips drop, policy security-ips drop, service http; classtype:trojan-activity; sid:31229; rev:1;)

The content from the PCAP is the following:
GET http://player.ooyala.com/static/modules/start_screen-fc89fba4b9d2b24da65dad518a40ede5c8441d7deeb4bf33d0c2ca747bedb700.swf HTTP/1.1
Host: player.ooyala.com<http://player.ooyala.com>
Proxy-Connection: keep-alive
User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/39.0.2171.99 Safari/537.36
X-Requested-With: ShockwaveFlash/<>
Accept: */*
Referer: http://www.skynews.com.au/news/top-stories/2016/02/04/coalition-mps-seek-turnbull-tax-answers.html
Accept-Encoding: gzip, deflate, sdch
Accept-Language: en-AU,en;q=0.8
Cookie: BCSI-CS-c87fda4ff6f22bb5=2; BCSI-CS-8d18d10a705be693=2; BCSI-CS-3d562a66fecc35f6=2

The kicker is that the IDS is showing a Translation Warning for this rule which states - "Ignored snort option(s): fast_pattern".

Looking into the pcre regex I cant seem to get it to match what the full HTTP GET request is (unless my regex troubleshooting is flawed), so I am assuming that the pcap is matching the "content" (/modules/) and with fast_pattern effectively off, its making a positive match based on the "content" alone and skipping over "pcre".

Would this assumption be correct? or is anyone able to tell me how rule processing would work with "content", "pcre" and "no fast_pattern" for this particular rule?

I hope I have been able to put the question clearly, if not please let me know.

Many thanks


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