alert tls $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE Observed Malicious SSL Cert (MosaicRegressor WinHTTP Downloader)"; flow:established,to_client; tls.cert_subject; content:"CN=ezan.yikongjian.cc"; bsize:21; fast_pattern; tls.cert_issuer; content:"C=CN, O=TrustAsia Technologies, Inc., OU=Domain Validated SSL, CN=TrustAsia TLS RSA CA"; bsize:86; reference:url,securelist.com/mosaicregressor/98849/; reference:url,74DB88B890054259D2F16FF22C79144D; classtype:domain-c2; sid:2030963; rev:1; metadata:attack_target Client_and_Server, created_at 2020_10_05, deployment Perimeter, performance_impact Low, confidence High, signature_severity Major, tag SSL_Malicious_Cert, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_10_05, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1071, mitre_technique_name Application_Layer_Protocol;)