ET MALWARE Observed Malicious SSL Cert (Cobalt Strike CnC)

alert tls $EXTERNAL_NET any -> $HOME_NET any (
    msg:"ET MALWARE Observed Malicious SSL Cert (Cobalt Strike CnC)";
    flow:established,to_client;
    tls.cert_subject;
    content:"CN=conwaytools.me"; bsize:17; fast_pattern;
    tls.cert_issuer;
    content:"C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3"; bsize:52;
    reference:url,twitter.com/bryceabdo/status/1308743381099646976;
    classtype:domain-c2;
    sid:2030902; rev:1;
    metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_and_Server, created_at 2020_09_23, deployment Perimeter, malware_family Cobalt_Strike, performance_impact Low, confidence High, signature_severity Major, tag SSL_Malicious_Cert, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_09_23, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1071, mitre_technique_name Application_Layer_Protocol;
)