ET ATTACK_RESPONSE KoiStealer Payload Inbound

Tim Peck@timpeck

•updated Nov 10, 2025•0•19

This rule detects the inbound transfer of a KoiStealer payload over HTTP. It specifically looks for unique string patterns within the HTTP response body that are indicative of the KoiStealer malware, including specific context definitions and keywords like 'CONTEXT_i386', 'CONTEXT_i486', 'CONTEXT_CONTROL', and 'CONTEXT_INTEGER'. This suggests the rule is designed to identify the download of the malware executable or a component of it.