alert tls $HOME_NET any -> $EXTERNAL_NET any (msg:"ET EXPLOIT_KIT Malicious TA2726 TDS Domain in TLS SNI (leatherbook .org)"; flow:established,to_server; tls.sni; bsize:15; content:"leatherbook.org"; fast_pattern; classtype:exploit-kit; sid:2057448; rev:2; metadata:affected_product Web_Browsers, attack_target Client_Endpoint, created_at 2024_11_14, deployment Perimeter, performance_impact Low, confidence High, signature_severity Critical, tag Exploit_Kit, tag TDS, tag compromised_website, tag TA2726, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2026_06_08, reviewed_at 2025_01_14;)