alert tls $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE Observed Targeted Attack Malicious SSL Cert (investbooking .de)"; flow:established,to_client; tls.cert_subject; content:"CN=investbooking.de"; bsize:19; fast_pattern; reference:url,blog.google/threat-analysis-group/new-campaign-targeting-security-researchers/; classtype:domain-c2; sid:2031550; rev:1; metadata:attack_target Client_and_Server, created_at 2021_01_26, deployment Perimeter, performance_impact Low, confidence High, signature_severity Major, tag SSL_Malicious_Cert, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2021_01_26, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1071, mitre_technique_name Application_Layer_Protocol;)