alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"ET INFO PDF Using CCITTFax Filter"; flow:established,to_client; content:"obj"; content:"<<"; within:4; content:"/CCITTFaxDecode"; distance:0; reference:url,nakedsecurity.sophos.com/2012/04/05/ccittfax-pdf-malware/; reference:url,blog.fireeye.com/research/2012/07/analysis-of-a-different-pdf-malware.html#more; classtype:bad-unknown; sid:2015561; rev:3; metadata:created_at 2012_08_02, confidence High, signature_severity Informational, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2019_07_26;)