alert tls $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE Observed Malicious SSL Cert (Gelsemium CnC)"; flow:established,to_client; tls.cert_subject; content:"C=US, ST=IH, L=IH, O=IH, OU=IH, CN=IH"; bsize:37; fast_pattern; tls.cert_issuer; content:"C=US, ST=CA, L=CA, O=CA, OU=CA, CN=CA"; bsize:37; reference:md5,87eb0975758ecef44e8368914cffe151; reference:url,www.welivesecurity.com/wp-content/uploads/2021/06/eset_gelsemium.pdf; classtype:domain-c2; sid:2033152; rev:1; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_and_Server, created_at 2021_06_21, deployment Perimeter, performance_impact Low, confidence High, signature_severity Major, tag SSL_Malicious_Cert, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2021_06_21, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1071, mitre_technique_name Application_Layer_Protocol;)