alert tls [$HOME_NET,$SMTP_SERVERS] any -> any any (msg:"ET MALWARE JS ZimReaper C2 DNS-label Exfiltration in TLS SNI"; flow:established,to_server; tls.sni; content:"d|2d|"; startswith; content:"|2e|i|2e|"; fast_pattern; pcre:"/d\x2d[a-z0-9]{10,12}(?:\x2e(?:2fa|c|e|p[aw]|url|v)\x2e[A-Z2-7]{1,60})+\x2ei\x2e[a-zA-Z0-9-]+\x2e[a-z]+/"; reference:url,www.proofpoint.com/us/blog/threat-insight/ta488-targets-zimbra-mailservers-half-click-exploits; classtype:domain-c2; sid:2071247; rev:1; metadata:attack_target Client_Endpoint, created_at 2026_07_21, deployment Perimeter, malware_family ZimReaper, confidence High, signature_severity Major, tag c2, updated_at 2026_07_21, mitre_tactic_id TA0010, mitre_tactic_name Exfiltration, mitre_technique_id T1048, mitre_technique_name Exfiltration_Over_Alternative_Protocol; target:src_ip;)