alert tcp $EXTERNAL_NET [1000,1001,1002] -> $HOME_NET any (msg:"ET MALWARE upStage Residential Proxy CnC Response"; flow:established,to_client; flowbits:isset,ET.upStage; dsize:<50; content:"ipsa"; depth:6; reference:url,www.malwarebytes.com/blog/threat-intel/2026/02/fake-7-zip-downloads-are-turning-home-pcs-into-proxy-nodes; reference:url,blog.lukeacha.com/2026/01/beware-of-fake-7zip-installer-upstage.html; classtype:trojan-activity; sid:2067603; rev:1; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, tls_state plaintext, created_at 2026_02_11, deployment Perimeter, performance_impact Low, confidence High, signature_severity Major, tag RAT, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2026_02_11, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel; target:dest_ip;)