alert tls $HOME_NET any -> $EXTERNAL_NET any (msg:"ET INFO Observed DNS over HTTPS Domain in TLS SNI (ns0 .fdn .fr)"; flow:established,to_server; tls.sni; content:"ns0.fdn.fr"; bsize:10; fast_pattern; classtype:misc-activity; sid:2045312; rev:3; metadata:affected_product Any, created_at 2023_05_03, deployment Perimeter, performance_impact Low, confidence High, signature_severity Informational, tag SSL_Malicious_Cert, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2024_12_01, reviewed_at 2024_10_01, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1572, mitre_technique_name Protocol_Tunneling;)