alert tls $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE Observed Malicious SSL/TLS Certificate (SilentLibrarian)"; flow:from_server,established; tls.cert_subject; content:"CN=login.cardiff.ac.erlib.me"; fast_pattern; classtype:domain-c2; sid:2037808; rev:2; metadata:attack_target Client_and_Server, created_at 2022_07_22, deployment Perimeter, performance_impact Low, confidence High, signature_severity Major, tag SSL_Malicious_Cert, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2023_03_13, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1071, mitre_technique_name Application_Layer_Protocol;)