alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE GemStone Gemini Chrome Extension CnC - Screenshots"; flow:established,to_server; http.uri; content:"/api/extensions/"; startswith; content:"/screenshots"; distance:32; endswith; http.header_names; to_lowercase; content:"x-extension-token|0d 0a|"; fast_pattern; http.request_body; strip_whitespace; content:"|7b 22|t|22 3a 22|"; content:"|22|keyword|22 3a 22|"; content:"|22|url|22 3a 22|"; content:"|22|dataUrl|22 3a 22|"; http.method; content:"POST"; reference:url,www.proofpoint.com/us/blog/threat-insight/once-bluemoon-multiple-state-aligned-threat-actors-rapidly-adopt-novel-exploit; classtype:command-and-control; sid:2071999; rev:1; metadata:attack_target Client_Endpoint, tls_state TLSDecrypt, created_at 2026_09_11, deployment Perimeter, malware_family GemStone, confidence High, signature_severity Major, tag c2, updated_at 2026_09_11, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1071, mitre_technique_name Application_Layer_Protocol;)