alert tls $HOME_NET any -> $EXTERNAL_NET any (msg:"ET INFO Observed DNS Over HTTPS Domain (dns .alidns .com in TLS SNI)"; flow:established,to_server; tls.sni; content:"dns.alidns.com"; bsize:14; fast_pattern; classtype:misc-activity; sid:2034912; rev:2; metadata:created_at 2022_01_13, deployment Perimeter, performance_impact Low, confidence High, signature_severity Informational, tag DoH, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2024_12_01, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1572, mitre_technique_name Protocol_Tunneling;)