alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET USER_AGENTS User-Agent (Unknown)"; flow:to_server,established; http.user_agent; content:"Unknown"; depth:7; endswith; classtype:trojan-activity; sid:2007991; rev:10; metadata:created_at 2010_07_30, confidence Medium, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_10_16;)