alert tls $EXTERNAL_NET any -> $HOME_NET any (
msg:"ET INFO Cisco Umbrella (OpenDNS) DNS Over HTTPS Certificate Inbound";
flow:established,to_client;
tls.cert_subject;
content:"CN=doh.familyshield.opendns.com"; bsize:31; 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:2039452; rev:1;
metadata:attack_target Client_Endpoint, created_at 2022_10_18, deployment Perimeter, confidence High, signature_severity Informational, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2022_10_18, reviewed_at 2024_12_02;
)