VBS_DUNIHI.YYR
VBS.Dunihi (Norton), Worm.VBS.Dinihou.ay (Kaspersky)
Windows
Threat Type: Worm
Destructiveness: No
Encrypted: Yes
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 executes commands from a remote malicious user, effectively compromising the affected system.
It gathers certain information on the affected computer.
TECHNICAL DETAILS
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 drops the following copies of itself into the affected system:
- %User Temp%\{malware file name and extension}
- %User Startup%\{malware file name and extension}
(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %User Startup% is the current user's Startup folder, which is usually C:\Documents and Settings\{user}\Start Menu\Programs\Startup on Windows 2000 and XP, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)
It drops the following files:
- {removable drive letter}:\{folder/file name}.lnk
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
{malware file name} = "wscript.exe //B "%User Temp%\{malware file name and extension}"
HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
{malware file name} = "wscript.exe //B "%User Temp%\{malware file name and extension}"
Other System Modifications
This Worm adds the following registry keys:
HKLM\SOFTWARE\{malware filename}
It adds the following registry entries as part of its installation routine:
HKEY_LOCAL_MACHINE\SOFTWARE\{malware file name}
(Default) = "{true or false (if executed from removable drive)} - {date of first execution}"
Propagation
This Worm drops the following copy(ies) of itself in all removable drives:
- {removable drive letter}:\{malware file name and extension}
Backdoor Routine
This Worm executes the following commands from a remote malicious user:
- excecute - Execute specified file
- update - Update malware code in %User Temp%\{malware file name and extension} and restart the malware
- uninstall - Uninstall the malware
- send - Download and run a file from the C&C server
- site-send - Download and run a file
- recv - Send a file to the C&C server
- enum-driver - Send list of drives
- enum-faf - Enumerate folders and files contained in a folder
- enum-process - List running processes
- cmd-shell - Execute a command using Command Prompt
- delete - Delete a file or folder
- exit-process - Terminate a process
- sleep - Running script sleeps
(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)
It connects to the following URL(s) to send and receive commands from a remote malicious user:
- http://fa{BLOCKED}ate.servequake.com:88/is-recving - Upload
- http://fa{BLOCKED}ate.servequake.com:88/is-sending - Download
- http://fa{BLOCKED}ate.servequake.com:88/is-ready - Report
Information Theft
This Worm gathers the following information on the affected computer:
- Volume serial number
- Computer name
- Current user name
- OS name
- Installed AV products
- USB spreading report
NOTES:
It drops .LNK files whose names correspond to the files and folders in the root directory of the removable drive then hides the original files and folders to trick users. When the .LNK files are double clicked, the dropped copy in the removable drive's root directory is executed.
SOLUTION
Step 1
Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.
Step 2
Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.
Step 3
Restart in Safe Mode
Step 4
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
- {malware file name} = "wscript.exe //B "%User Temp%\{malware file name and extension}"
- {malware file name} = "wscript.exe //B "%User Temp%\{malware file name and extension}"
- In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
- {malware file name} = "wscript.exe //B "%User Temp%\{malware file name and extension}"
- {malware file name} = "wscript.exe //B "%User Temp%\{malware file name and extension}"
Step 5
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
- {malware filename}
- {malware filename}
Step 6
Search and delete this file
- {removable drive letter}:\{folder/file name}.lnk
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as VBS_DUNIHI.YYR. 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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