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Re: UTF-8 BOM
From: Joel Esler <jesler () sourcefire com>
Date: Tue, 9 Apr 2013 17:17:41 -0400

Yup. Caught those already. I'm testing them. 

--
Joel Esler
Sent from my iPhone 

On Apr 9, 2013, at 3:06 PM, rmkml <rmkml () yahoo fr> wrote:

Hi,

Thx for sharing,

-maybe change B4 to 4B ?

-for http sig, maybe add H on pcre ?

Best Regards
Rmkml


On Mon, 8 Apr 2013, Joel Esler wrote:

On Apr 8, 2013, at 4:22 PM, James Lay <jlay () slave-tothe-box net> 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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