VBS_AUTORUN.MJSM
Windows 2000, Windows XP, Windows Server 2003
![](/vinfo/imgFiles/legend.jpg)
Threat Type: Worm
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
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
Arrival Details
This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
Installation
This worm drops the following copies of itself into the affected system:
- %Windows%\Thumbs.vbs
(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)
Autostart Technique
This worm adds the following registry entries to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
avctrl = "wscript.exe %Windows%\Thumbs.vbs"
Other System Modifications
This worm modifies the following registry entries:
HKEY_CLASSES_ROOT\VBSFile
@ = "Configuration Script"
(Note: The default value data of the said registry entry is VBSCript Script File.)
HKEY_CLASSES_ROOT\VBSFile\DefaultIcon
@ = "%SystemRoot%\System32\shell32.dll,-154"
(Note: The default value data of the said registry entry is %SystemRoot%\System32\wscript.exe,2.)
Propagation
This worm drops the following copy of itself in all physical and removable drives:
- Thumbs.vbs
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=wscript.exe Thumbs.vbs
icon=0
shell\install = &Install
shell\install\command = wscript.exe Thumbs.vbs
shell\uninstall = &UnInstall
shell\uninstall\command = wscript.exe Thumbs.vbs
shell\readme = &Read Me
shell\readme\command = wscript.exe Thumbs.vbs
shell\help = &Help
shell\help\command = wscript.exe Thumbs.vbs
shell\Open = &Open
shell\Open\command = wscript.exe Thumbs.vbs
shell\Open\Default=1
shell\Run = &Run
shell\Run\command = wscript.exe Thumbs.vbs
shell\Run\Default=1
shell\explore=Explorer
shell\explore\Command=Explorer.exe
SOLUTION
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
Terminate a malware/grayware process
*Note: If the detected process is not displayed in theWindows Task Manager, continue doing the next steps.
- WSCRIPT.EXE
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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
- avctrl = "wscript.exe %Windows%\Thumbs.vbs"
- avctrl = "wscript.exe %Windows%\Thumbs.vbs"
Step 4
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_CLASSES_ROOT\VBSFile
- From: @ = "Configuration Script"
To: @ = "VBSCript Script File"
- From: @ = "Configuration Script"
- In HKEY_CLASSES_ROOT\VBSFile\DefaultIcon
- From: @ = "%SystemRoot%\System32\shell32.dll,-154"
To: @ = "%SystemRoot%\System32\wscript.exe,2"
- From: @ = "%SystemRoot%\System32\shell32.dll,-154"
Step 5
Search and delete AUTORUN.INF files created by VBS_AUTORUN.MJSM that contain these strings
Step 6
Scan your computer with your Trend Micro product to delete files detected as VBS_AUTORUN.MJSM. 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.
Did this description help? Tell us how we did.