Rule History

alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"ET ATTACK_RESPONSE KoiStealer Payload Inbound"; flow:established,to_client; http.response_body; content:"Add|2d|Type|20 2d|TypeDefinition|20 40|"; startswith; fast_pattern; content:"|20 20 20|CONTEXT|5f|i386|20 3d 20|0x10000"; content:"|20 20 20|CONTEXT|5f|i486|20 3d 20|0x10000|2c 20 20 20 2f 2f 20 20|same|20|as|20|i386"; content:"CONTEXT_CONTROL"; content:"CONTEXT_INTEGER"; classtype:trojan-activity; sid:2064144; rev:1; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, tls_state plaintext, created_at 2025_08_25, deployment Perimeter, malware_family KoiStealer, confidence Medium, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2025_08_25, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1105, mitre_technique_name Ingress_Tool_Transfer; target:dest_ip;)