alert tls $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE Malicious CobaltStrike SSL/TLS Certificate Observed"; flow:established,to_client; tls.cert_serial; content:"33:00:14:46:13:a5:f5:e2:96:09:bb:55:f2:00:00:00:14:46:13"; fast_pattern; classtype:domain-c2; sid:2055755; rev:1; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, affected_product Windows_11, attack_target Client_and_Server, tls_state TLSEncrypt, created_at 2024_09_05, deployment Perimeter, malware_family CobaltStrike, performance_impact Low, confidence High, signature_severity Major, tag SSL_Malicious_Cert, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2024_09_05, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1071, mitre_technique_name Application_Layer_Protocol; target:dest_ip;)