alert tls $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE Observed Malicious SSL Cert (Cobalt Strike)"; flow:established,to_client; tls.cert_subject; content:"CN=systemmentorsec.com"; bsize:22; fast_pattern; reference:url,twitter.com/Unit42_Intel/status/1440027013595766784; reference:url,www.malware-traffic-analysis.net/2021/09/20/index.html; classtype:domain-c2; sid:2033993; rev:1; metadata:attack_target Client_and_Server, created_at 2021_09_21, deployment Perimeter, malware_family Cobalt_Strike, performance_impact Low, confidence High, signature_severity Major, tag SSL_Malicious_Cert, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2021_09_21, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1071, mitre_technique_name Application_Layer_Protocol;)