WORM_AUTORUN.ZZI
Windows 2000, XP, Server 2003
Threat Type: Worm
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
This worm arrives by connecting affected removable drives to a system. It arrives via removable drives.
It modifies registry entries to hide files with System and Read-only attributes.
It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.
TECHNICAL DETAILS
167,936 bytes
EXE
Yes
14 Oct 2010
Arrival Details
This worm arrives by connecting affected removable drives to a system.
It arrives via removable drives.
Installation
This worm drops the following copies of itself into the affected system:
- %User Temp%doscp.exe
- {drive}:\nb3wbk.exe
(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003.)
It drops the following component file(s):
- %User Temp%\doscp0.dll - also detected as WORM_AUTORUN.ZZI
(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003.)
It injects threads into the following normal process(es):
- Explorer.exe
Autostart Technique
This worm adds the following registry entries to enable its automatic execution at every system startup:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
doscp = %User Temp%\doscp.exe
Other System Modifications
This worm adds the following registry keys as part of its installation routine:
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\MADOWN
HKEY_CLASSSES_ROOT\CLSID\MADOWN
It modifies the following registry entries to hide files with System and Read-only attributes:
HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = 2
(Note: The default value data of the said registry entry is 1.)
HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
ShowSuperHidden = 0
(Note: The default value data of the said registry entry is 1.)
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced\Folder\Hidden\
SHOWALL
CheckedValue = 0
(Note: The default value data of the said registry entry is 1.)
Propagation
This worm drops the following copy(ies) of itself in all removable drives:
- 8a.exe
It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.
The said .INF file contains the following strings:
[AutoRun]
open=nb3wbk.exe
shell\open\Command=nb3wbk.exe
Dropping Routine
This worm sets the attributes of its dropped file(s) to the following:
- Hidden
- Read-Only
- System
- Hidden
- Read-Only
- System
SOLUTION
8.900
Step 1
For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.
Step 2
Restart in Safe Mode
Step 3
Delete this registry value
Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- doscp=%User Temp%\doscp.exe
- doscp=%User Temp%\doscp.exe
Step 4
Delete this registry key
Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID
- MADOWN
- MADOWN
- In HKEY_CLASSSES_ROOT\CLSID\
- MADOWN
- MADOWN
Step 5
Restore this modified registry value
Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.
- In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced
- From: Hidden = 2
To: 1
- From: Hidden = 2
- In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced
- From: ShowSuperHidden = 0
To: 1
- From: ShowSuperHidden = 0
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Folder\Hidden\SHOWALL
- From: CheckedValue = 0
To: 1
- From: CheckedValue = 0
Step 6
Search and delete AUTORUN.INF files created by WORM_AUTORUN.ZZI that contain these strings
[AutoRun]
open=nb3wbk.exe
shell\open\Command=nb3wbk.exe
Step 7
Scan your computer with your Trend Micro product to delete files detected as WORM_AUTORUN.ZZI. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.
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