alert smtp $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Win32/HackTool.Agent.CS SMTP activity"; flow:established,to_server; content:"|7c 7c 7c|hhjjkk"; fast_pattern; threshold:type limit, count 5, seconds 300, track by_src; classtype:trojan-activity; sid:2037755; rev:1; metadata:attack_target SMTP_Server, created_at 2022_07_13, deployment Perimeter, malware_family Win32_HackTool_Agent_CS, performance_impact Low, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2022_07_13;)