alert tls $HOME_NET any -> $EXTERNAL_NET any (msg:"ET INFO Observed SoftEther VPN Service Domain (softether .org in TLS SNI)"; flow:established,to_server; tls.sni; dotprefix; content:".softether.org"; endswith; fast_pattern; reference:url,www.softether.org/4-docs/1-manual; classtype:misc-activity; sid:2068202; rev:1; metadata:affected_product Any, attack_target Client_and_Server, created_at 2026_03_13, deployment Perimeter, performance_impact Low, confidence High, signature_severity Informational, tag VPN, tag SoftEther, updated_at 2026_03_13, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1219, mitre_technique_name Remote_Access_Software;)