alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Brontok User-Agent Detected (Rivest)"; flow:established,to_server; http.user_agent; content:"Rivest"; depth:6; endswith; nocase; reference:md5,c83b55ab56f3deb60858cb25d6ded8c4; classtype:trojan-activity; sid:2020179; rev:4; metadata:created_at 2015_01_13, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_10_14;)