alert tls $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Observed CobaltStrike CnC Domain (krinsop .com in TLS SNI)"; flow:established,to_server; tls.sni; content:"krinsop.com"; bsize:11; fast_pattern; reference:url,thedfirreport.com/2021/07/19/icedid-and-cobalt-strike-vs-antivirus/; reference:md5,2232b445760712242a0e5ea456fcc700; classtype:domain-c2; sid:2033392; rev:1; metadata:attack_target Client_Endpoint, created_at 2021_07_23, deployment Perimeter, malware_family Cobalt_Strike, confidence High, signature_severity Major, updated_at 2021_07_23, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1001, mitre_technique_name Data_Obfuscation;)