alert tls $EXTERNAL_NET any -> $HOME_NET any (msg:"ET INFO Ordns DNS Over HTTPS Certificate Inbound"; flow:established,to_client; threshold:type limit, track by_src, count 1, seconds 300; tls.cert_subject; content:"CN=ordns.he.net"; endswith; fast_pattern; reference:url,developers.cloudflare.com/1.1.1.1/dns-over-https/request-structure/; classtype:misc-activity; sid:2035859; rev:2; metadata:created_at 2022_04_07, deployment Perimeter, confidence High, signature_severity Minor, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2022_04_07;)