alert tls $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE Observed Malicious SSL Cert (MageCart Group 4 CnC)"; flow:from_server,established; tls.cert_subject; content:"CN=s1all.com"; nocase; endswith; tls.cert_issuer; content:"C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3"; reference:url,community.riskiq.com/projects/67ba07d8-49e0-3239-80d0-668b3c096240; classtype:domain-c2; sid:2027013; rev:3; metadata:affected_product Web_Browsers, attack_target Client_and_Server, created_at 2019_02_28, deployment Perimeter, malware_family MageCart, performance_impact Low, confidence High, signature_severity Major, tag SSL_Malicious_Cert, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_09_16, mitre_tactic_id TA0042, mitre_tactic_name Resource_Development, mitre_technique_id T1587, mitre_technique_name Develop_Capabilities;)