alert tls $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE Malicious SSL certificate detected (Possible Sinkhole)"; flow:established,to_client; tls.cert_subject; content:"O=infosec.jp"; fast_pattern; content:"CN=www.infosec.jp"; content:"snowyowl@jpnsec.com"; distance:0; reference:md5,ef5fa2378307338d4e75dece88158d77; classtype:domain-c2; sid:2022323; rev:3; metadata:attack_target Client_and_Server, created_at 2016_01_01, deployment Perimeter, performance_impact Low, confidence Medium, signature_severity Major, tag SSL_Malicious_Cert, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2022_03_24, reviewed_at 2024_04_16, mitre_tactic_id TA0042, mitre_tactic_name Resource_Development, mitre_technique_id T1587, mitre_technique_name Develop_Capabilities;)