ET MALWARE Observed Malicious SSL Cert (APT32 CnC)

Query · suricata

flow:from_server,established;
tls.cert_subject;
content:"CN=check.homeip.net"; nocase; endswith;
tls.cert_issuer;
content:"C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3";
Raw source ET MALWARE Observed Malicious SSL Cert (APT32 CnC) · Suricata
Esc
Published by Emerging Threats Open ↗, licensed under BSD 3-Clause ↗. Line breaks added for readability; the rule is otherwise unchanged. 
alert tls $EXTERNAL_NET any -> $HOME_NET any (
    msg:"ET MALWARE Observed Malicious SSL Cert (APT32 CnC)";
    flow:from_server,established;
    tls.cert_subject;
    content:"CN=check.homeip.net"; nocase; endswith;
    tls.cert_issuer;
    content:"C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3";
    reference:url,unit42.paloaltonetworks.com/tracking-oceanlotus-new-downloader-kerrdown/;
    classtype:domain-c2;
    sid:2026872; rev:3;
    metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_and_Server, created_at 2019_02_01, deployment Perimeter, malware_family KerrDown, performance_impact Low, confidence High, signature_severity Major, tag SSL_Malicious_Cert, tag APT32, 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;
)

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