alert tls $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Observed TA444 Domain in TLS SNI (docsend .linkpc .net)"; flow:established,to_server; tls.sni; dotprefix; content:".docsend.linkpc.net"; endswith; fast_pattern; reference:url,www.elastic.co/security-labs/DPRK-strikes-using-a-new-variant-of-rustbucket; classtype:trojan-activity; sid:2046708; rev:1; metadata:attack_target Client_Endpoint, created_at 2023_06_28, deployment Perimeter, confidence High, signature_severity Major, tag SSL_Malicious_Cert, tag TA444, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2023_06_30, former_sid 2854711, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1071, mitre_technique_name Application_Layer_Protocol; target:src_ip;)