alert tls $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Observed StrongPity CnC Domain in TLS SNI"; flow:established,to_server; tls.sni; bsize:23; content:"upd3-srv-system-app.com"; reference:url,blog.talosintelligence.com/2020/06/promethium-extends-with-strongpity3.html; classtype:domain-c2; sid:2030426; rev:3; metadata:affected_product Web_Browsers, created_at 2020_07_01, deployment Perimeter, performance_impact Low, confidence High, signature_severity Major, tag StrongPity, tag SSL_TLS_SNI, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2024_03_25, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1071, mitre_technique_name Application_Layer_Protocol;)