alert tls $HOME_NET any -> $EXTERNAL_NET any (msg:"ET INFO Suspicious Domain (*.cf) in TLS SNI"; flow:established,to_server; threshold:type limit, count 1, track by_src, seconds 120; tls.sni; content:".cf"; endswith; fast_pattern; nocase; classtype:misc-activity; sid:2025111; rev:6; metadata:created_at 2017_12_03, confidence Medium, signature_severity Informational, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2022_12_01;)