[Snort-sigs] UTF-8 BOM

Joel Esler jesler at ...435...
Mon Apr 8 17:13:45 EDT 2013


On Apr 8, 2013, at 4:22 PM, James Lay <jlay at ...3266...> wrote:
> On 2013-04-08 14:10, Joel Esler wrote:
>> How about something like this James?  (Three rules)
>> 
>> 
>> alert tcp $EXTERNAL_NET any -> $SMTP_SERVERS 25 (msg:"MALWARE-OTHER
>> UTF-8 BOM in zip file attachment detected";
>> flow:to_server,established; content:".zip"; fast_pattern:only;
>> content:"Content-Disposition: attachment|3B|"; content:"filename=";
>> nocase; pcre:"/filename=[^\n]*?\x2ezip[\x22\x27\s]/si"; file_data;
>> content:"|EF BB BF 50 B4|"; depth:5; metadata:policy balanced-ips
>> drop, policy security-ips drop, ruleset community, service smtp;
>> reference:url,http://blogs.mcafee.com/mcafee-labs/phishing-threat-uses-utf-8-bom-in-zip-signature-to-evade-detection;
>> classtype:trojan-activity;)
>> 
>> alert tcp $EXTERNAL_NET [110,143] -> $HOME_NET any
>> (msg:"MALWARE-OTHER UTF-8 BOM in zip file attachment detected";
>> flow:to_client,established; content:".zip"; fast_pattern:only;
>> content:"Content-Disposition: attachment|3B|"; content:"filename=";
>> nocase; pcre:"/filename=[^\n]*?\x2ezip[\x22\x27\s]/si"; file_data;
>> content:"|EF BB BF 50 B4|"; depth:5; metadata:policy balanced-ips
>> drop, policy security-ips drop, ruleset community, service imap,
>> service pop3;
>> reference:url,http://blogs.mcafee.com/mcafee-labs/phishing-threat-uses-utf-8-bom-in-zip-signature-to-evade-detection;
>> classtype:trojan-activity;)
>> 
>> alert tcp $EXTERNAL_NET $HTTP_PORTS -> $HOME_NET any
>> (msg:"MALWARE-OTHER UTF-8 BOM in zip file attachment detected";
>> flow:to_client,established; content:".zip"; fast_pattern:only;
>> http_header; content:"filename="; nocase; http_header;
>> pcre:"/filename=[^\n]*?\x2ezip[\x22\x27\s]/si"; file_data;
>> content:"|EF BB BF 50 B4|"; depth:5; metadata:policy balanced-ips
>> drop, policy security-ips drop, ruleset community, service http;
>> reference:url,http://blogs.mcafee.com/mcafee-labs/phishing-threat-uses-utf-8-bom-in-zip-signature-to-evade-detection;
>> classtype:trojan-activity;)
>> 
> 
> Dammit Joel...you're always look so much better than mine :P  As always, thanks a bunch :)

:D

Alright, I have these in the test system, let's see how they do.

--
Joel Esler
Senior Research Engineer, VRT
OpenSource Community Manager
Sourcefire
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