alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE FakeAV Check-in purporting to be MSIE with invalid terse HTTP headers"; flow:established,to_server; http.user_agent; content:"Mozilla/4.0|20|(compatible|3b 20|MSIE|20|"; depth:30; http.request_body; content:"data="; depth:5; fast_pattern; http.accept; content:"*/*"; depth:3; endswith; http.content_type; content:"application/x-www-form-urlencoded"; depth:33; endswith; http.header_names; content:"|0d 0a|Accept|0d 0a|Content-Type|0d 0a|Host|0d 0a|"; depth:30; content:"User-Agent|0d 0a|"; distance:0; content:"Content-Length|0d 0a|"; distance:0; classtype:trojan-activity; sid:2012627; rev:5; metadata:created_at 2011_04_04, confidence Medium, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_09_15;)