ET POLICY Observed SSL Cert (DoH Service)

Query · suricata

flow:from_server,established;
tls.cert_subject;
content:"CN=www.rubyfish.cn"; nocase; fast_pattern; endswith;
tls.cert_issuer;
content:"C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3";
Raw source ET POLICY Observed SSL Cert (DoH Service) · 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 POLICY Observed SSL Cert (DoH Service)";
    flow:from_server,established;
    tls.cert_subject;
    content:"CN=www.rubyfish.cn"; nocase; fast_pattern; endswith;
    tls.cert_issuer;
    content:"C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3";
    classtype:policy-violation;
    sid:2029051; rev:3;
    metadata:created_at 2019_11_21, deployment Perimeter, performance_impact Low, confidence High, signature_severity Minor, tag DNS_over_HTTPS, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_10_22, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1572, mitre_technique_name Protocol_Tunneling;
)

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