alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Win32/Koi Stealer CnC Checkin (GET)"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"php|3f|id|3d 26|subid|3d|"; fast_pattern; pcre:"/^[a-zA-Z0-9]{8}$/R"; reference:url,malware-traffic-analysis.net/2025/01/23/index.html; classtype:command-and-control; sid:2059750; rev:2; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, tls_state plaintext, created_at 2025_01_29, deployment Perimeter, malware_family KoiStealer, confidence High, signature_severity Major, tag c2, updated_at 2025_07_11, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1071, mitre_technique_name Application_Layer_Protocol; target:src_ip;)