alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Joanap CnC Checkin"; flow:to_server,established; http.uri; content:".ico"; http.user_agent; content:"Mozillar"; depth:8; fast_pattern; http.header_names; content:!"Referer|0d 0a|"; reference:url,securelist.com/blog/incidents/73914/operation-blockbuster-revealed/; reference:url,operationblockbuster.com/resources/index.html; classtype:command-and-control; sid:2021730; rev:4; metadata:created_at 2015_08_31, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_07_14;)