alert tls $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Observed Kimsuky Domain in TLS SNI"; flow:established,to_server; tls.sni; bsize:16; content:"ygbsbl.hopto.org"; fast_pattern; reference:url,aryaka.com/blog/kimsuky-apt-stealth-malware-social-engineering; classtype:command-and-control; sid:2063840; rev:1; metadata:attack_target Client_Endpoint, created_at 2025_06_24, deployment Perimeter, malware_family Kimsuky, confidence High, signature_severity Major, tag SSL_Malicious_Cert, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2025_07_31, former_sid 2863022;)