Hackers now use ZIP file concatenation to evade detection

Perception Point discovered a phishing campaign that hid a Windows trojan inside concatenated ZIP archives—multiple ZIP files appended together so some archive tools show only benign contents while others reveal the malicious executable. The report explains how 7zip, WinRAR, and Windows File Explorer differ in handling concatenated ZIPs, demonstrates the evasion implications, and recommends defenses like security solutions with recursive unpacking and stricter email/archive filtering.