alert tls $EXTERNAL_NET any -> $HOME_NET any (msg:"ET INFO AhaDNS DNS Over HTTPS Certificate Inbound"; flow:established,to_client; tls.cert_subject; content:"CN=blitz.ahadns.com "; bsize:20; fast_pattern; threshold:type both, count 1, seconds 600, track by_src; reference:url,github.com/curl/curl/wiki/DNS-over-HTTPS; classtype:misc-activity; sid:2039434; rev:3; metadata:attack_target Client_Endpoint, created_at 2022_10_18, deployment Perimeter, confidence High, signature_severity Informational, tag DoH, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2024_01_31;)