alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET USER_AGENTS Suspicious User-Agent (firefox)"; flow:established,to_server; http.user_agent; bsize:7; content:"firefox"; fast_pattern; reference:url,unit42.paloaltonetworks.com/oilrig-novel-c2-channel-steganography/; classtype:trojan-activity; sid:2030623; rev:2; metadata:attack_target Client_Endpoint, created_at 2020_07_30, deployment Perimeter, performance_impact Low, confidence High, signature_severity Informational, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2024_03_24;)