alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Cobalt Strike Malleable C2 Profile (bg)"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/bg"; bsize:3; http.cookie; content:"SSID="; startswith; fast_pattern; pcre:"/^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{4})$/R"; reference:md5,5b5a730628dc9eba2c12530d225c2f70; classtype:command-and-control; sid:2032966; rev:2; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2021_05_17, deployment Perimeter, malware_family Cobalt_Strike, malware_family Cobalt_Strike, confidence Medium, signature_severity Major, updated_at 2021_05_17, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1001, mitre_technique_name Data_Obfuscation;)