WORM_SILLY.MBA
Windows 2000, Windows XP, Windows Server 2003

Threat Type: Worm
Destructiveness: No
Encrypted: No
In the wild: Yes
OVERVIEW
This worm arrives via removable drives. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
It modifies registry entries to hide files with System and Read-only attributes.
It drops copies of itself in all removable drives.
TECHNICAL DETAILS
294,912 bytes
EXE
Yes
13 Sep 2011
Arrival Details
This worm arrives via removable drives.
It 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 adds the following folders:
- %Windows%\log
- %Program Files%\Common Files\log
(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.. %Program Files% is the default Program Files folder, usually C:\Program Files.)
It drops the following files:
- %Windows%\drive.ini
- %User Temp%\xx12
- %User Temp%\xx13
- %User Temp%\xx14
- %User Temp%\xx15
- %User Temp%\xx16
- %User Temp%\alldetails.txt
- %Program Files%\Common Files\log\WINXP\{Random File Name}.cab.bak
(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.. %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.. %Program Files% is the default Program Files folder, usually C:\Program Files.)
It drops the following copies of itself into the affected system:
- %Program Files%\Common Files\svchost.exe
(Note: %Program Files% is the default Program Files folder, usually C:\Program Files.)
Autostart Technique
This worm modifies the following registry entry(ies) to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Userinit = "%System%\userinit.exe,%Program Files%\Common Files\svchost.exe -s"
(Note: The default value data of the said registry entry is %System%\userinit.exe,.)
Other System Modifications
This worm modifies the following registry entries to hide files with System and Read-only attributes:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced\Folder\Hidden\
SHOWALL
CheckedValue = "0x00000001 (1)"
(Note: The default value data of the said registry entry is 1.)
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced\Folder\HideFileExt
UncheckedValue = "0x00000000 (0)"
(Note: The default value data of the said registry entry is 0.)
Propagation
This worm drops copies of itself in all removable drives.
SOLUTION
9.200
8.424.08
13 Sep 2011
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
Identify and delete files detected as WORM_SILLY.MBA using the Recovery Console
Step 3
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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
- From: Userinit = "%System%\userinit.exe,%Program Files%\Common Files\svchost.exe -s"
To: Userinit = "%System%\userinit.exe,"
- From: Userinit = "%System%\userinit.exe,%Program Files%\Common Files\svchost.exe -s"
Step 4
Restore modified and/or deleted registry value/s using this VBScirpt
To restore the modified and/or deleted registry value/s:
- Open Notepad.
» For Windows 2000, Windows XP, and Windows Server 2003 users, click Start>Run. In the Open input box, type notepad then press Enter.
» For Windows Vista and Windows 7 users, click Start, type notepad in the Search input field then press Enter. - Copy and paste the following script:
- Save this file as C:\RESTORE.VBS.
- Run C:\RESTORE.VBS.
» For Windows 2000, XP, and Server 2003 users, click Start>Run. In the Open input box, type C:\RESTORE.VBS then press Enter.
» For Windows Vista and Windows 7 users, click Start, type C:\RESTORE.VBS in the Search input field then press Enter.
Step 5
Search and delete these folders
- %Windows%\log
- %Program Files%\Common Files\log
Step 6
Search and delete these files
- %Windows%\drive.ini
- %User Temp%\xx12
- %User Temp%\xx13
- %User Temp%\xx14
- %User Temp%\xx15
- %User Temp%\xx16
- %User Temp%\alldetails.txt
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_SILLY.MBA. 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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