ET HUNTING Observed Let's Encrypt Certificate for Suspicious TLD (.xyz)

Query · suricata

flow:established,to_client;
tls.cert_subject;
content:".xyz"; endswith;
tls.cert_issuer;
content:"Let's Encrypt";
Raw source ET HUNTING Observed Let's Encrypt Certificate for Suspicious TLD (.xyz) · 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 HUNTING Observed Let's Encrypt Certificate for Suspicious TLD (.xyz)";
    flow:established,to_client;
    tls.cert_subject;
    content:".xyz"; endswith;
    tls.cert_issuer;
    content:"Let's Encrypt";
    classtype:bad-unknown;
    sid:2025194; rev:3;
    metadata:attack_target Client_Endpoint, created_at 2018_01_09, deployment Perimeter, confidence Medium, signature_severity Minor, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_09_16;
)

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