alert tls $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Observed CobaltStrike CnC Domain (gmbfrom .com in TLS SNI)"; flow:established,to_server; tls.sni; bsize:11; content:"gmbfrom.com"; fast_pattern; reference:url,thedfirreport.com/2021/07/19/icedid-and-cobalt-strike-vs-antivirus/; classtype:domain-c2; sid:2033394; rev:2; metadata:attack_target Client_Endpoint, created_at 2021_07_23, deployment Perimeter, malware_family Cobalt_Strike, confidence High, signature_severity Major, updated_at 2024_03_25, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1001, mitre_technique_name Data_Obfuscation;)