ET INFO UncensoredDNS DNS Over HTTPS Certificate Inbound

Query · suricata

flow:established,to_client;
tls.cert_subject;
content:"CN="; startswith;
content:".anycast.censurfridns.dk"; endswith; fast_pattern;
threshold:type both, count 1, seconds 600, track by_src;
Raw source ET INFO UncensoredDNS DNS Over HTTPS Certificate Inbound · Suricata
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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 INFO UncensoredDNS DNS Over HTTPS Certificate Inbound";
    flow:established,to_client;
    tls.cert_subject;
    content:"CN="; startswith;
    content:".anycast.censurfridns.dk"; endswith; fast_pattern;
    threshold:type both, count 1, seconds 600, track by_src;
    reference:url,blog.uncensoreddns.org/dns-servers/;
    classtype:misc-activity;
    sid:2035154; rev:1;
    metadata:attack_target Client_Endpoint, created_at 2022_02_09, deployment Perimeter, performance_impact Low, confidence High, signature_severity Informational, tag DoH, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2022_02_09;
)

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