alert tls $HOME_NET any -> $EXTERNAL_NET any (msg:"ET INFO Observed DNS Over HTTPS Domain (agh .kul-lippek .de in TLS SNI)"; flow:established,to_server; tls.sni; bsize:17; content:"agh.kul-lippek.de"; fast_pattern; reference:url,github.com/curl/curl/wiki/DNS-over-HTTPS; classtype:misc-activity; sid:2049445; rev:4; metadata:created_at 2023_12_04, deployment Perimeter, performance_impact Low, confidence High, signature_severity Informational, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2024_12_01, reviewed_at 2024_01_03, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1572, mitre_technique_name Protocol_Tunneling;)