Worm:W32/Zimuse.A

Classification

Category:

Malware

Platform:

W32

Type:

Worm

Aliases:

Worm.Win32.Mseus.a
Dropped:Worm.Zimuse.A
Worm:W32/Zimuse.A
Trojan.Generic.1729691
Win32/Zimuse.A (Other)
Worm:Win32/Zumes.A!sys (Microsoft)

Summary

Zimuse is a family of worms that performs destructive overwrite of the Master Boot Record of disk drives on the infected system.

Removal

Technical Details

General

Arrival to the system

Zimuse.A arrives on the system either as a standalone file (possibly from a malicious download or email) or by infected removable devices (e.g., USB sticks).

When executed, it will display a fake WinZip dialog box (see image below). This dialog box is a sham. Regardless of the user's subsequent interaction, the worm has already infected the system.

The following file operations will be performed on the system:

Creates these files:
Uses these temporary files:

Launchpoint/Autostart

Uses registry launchpoints to ensure its components run or are loaded as services on every startup (see below).

Registry Changes

Creates these keys:

HKLM\System\CurrentControlSet\Services\EventLog\System\MSTART
HKLM\System\CurrentControlSet\Services\MSTART
HKLM\System\CurrentControlSet\Services\MSTART\Security
HKLM\System\CurrentControlSet\Services\Mseu
HKLM\system\currentcontrolset\services\UnzipService

Sets these values:

HKLM\System\CurrentControlSet\Services\EventLog\System\MSTART EventMessageFile = %SystemRoot%\System32\Drivers\MSTART.SYS
HKLM\System\CurrentControlSet\Services\EventLog\System\MSTART TypesSupported = 7
HKLM\System\CurrentControlSet\Services\MSTART Type = 1
HKLM\System\CurrentControlSet\Services\MSTART Start = 3
HKLM\System\CurrentControlSet\Services\MSTART ErrorControl = 1
HKLM\System\CurrentControlSet\Services\MSTART ImagePath = \??\C:\WINDOWS\system32\Drivers\MSTART.SYS [Launchpoint: Service]
HKLM\System\CurrentControlSet\Services\MSTART DisplayName = MSTART
HKLM\System\CurrentControlSet\Services\MSTART\Security Security =
HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run Dump = C:\Program files\Dump\Dump.exe [Launchpoint: Run]
HKLM\System\CurrentControlSet\Services\Mseu Type = 1
HKLM\System\CurrentControlSet\Services\Mseu Start = 2
HKLM\System\CurrentControlSet\Services\Mseu ErrorControl = 1
HKLM\System\CurrentControlSet\Services\Mseu Tag = 1
HKLM\System\CurrentControlSet\Services\Mseu Group = Extended base
HKLM\system\currentcontrolset\services\UnzipService Type = 272
HKLM\system\currentcontrolset\services\UnzipService Start = 2
HKLM\system\currentcontrolset\services\UnzipService ImagePath = System32\Mseus.exe [Launchpoint: Service]
HKLM\system\currentcontrolset\services\UnzipService ErrorControl = 0
HKLM\system\currentcontrolset\services\UnzipService DisplayName = Self extract service
HKLM\system\currentcontrolset\services\UnzipService ObjectName = LocalSystem
HKLM\system\currentcontrolset\services\UnzipService Description = Self extract archive decrypt

Infection

After a certain time period from the initial infection, the worm will infect removable drives inserted into the system by dropping a copy of itself named zipsetup.exe and an autorun.inf file as show below:

[autorun] shellexecute=zipsetup.exe /H

Payload

After a further period of dormancy, the worm will trigger its payload, which overwrites the Master Boot Record of available drives on the system, and effectively crippling the file system and rendering data on the disk inaccessible except with specialist tools. The following dialog box will be displayed: