Winsage
January 29, 2026
Praetorian Inc. has launched Swarmer, a tool that enables low-privilege attackers to maintain stealthy persistence in the Windows registry while avoiding detection by Endpoint Detection and Response (EDR) systems. Swarmer uses mandatory user profiles and the Offline Registry API to modify the NTUSER hive without triggering standard registry hooks. It operates by creating an NTUSER.MAN file that replaces the NTUSER.DAT hive upon user login, allowing low-privilege users to manipulate registry settings without alerting EDR tools. Swarmer employs functions from Microsoft’s Offline Registry Library, enabling it to perform operations without invoking Reg* API calls, thus evading detection mechanisms.
Swarmer's workflow involves exporting the HKCU registry, modifying it, and executing the tool with specific commands to place the modified NTUSER.MAN file into the user profile. It can be used as an executable or a PowerShell module. While it presents a novel method for persistence, Swarmer has limitations, such as being unable to update without admin access and requiring user login to activate. Detection strategies include monitoring for NTUSER.MAN file creation and Offreg.dll usage in non-standard processes.
