alert tls $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE Observed Malicious SSL Cert (CoreBot C2)"; flow:established,from_server; tls.cert_subject; content:"CN=ok.investments"; fast_pattern; nocase; reference:md5,75368c9240a3c238aa3b5518906a3cdb; classtype:domain-c2; sid:2025485; rev:4; metadata:attack_target Client_and_Server, created_at 2018_04_11, deployment Perimeter, performance_impact Low, confidence High, signature_severity Major, tag SSL_Malicious_Cert, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_08_25, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1071, mitre_technique_name Application_Layer_Protocol;)