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.nu"; endswith; fast_pattern; threshold:type both, count 1, seconds 600, track by_src; reference:url,blog.uncensoreddns.org/dns-servers/; classtype:misc-activity; sid:2035155; 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;)