VBS_DUNIHI.AUM
Worm:VBS/Jenxcus.BB (Microsoft), VBS.Dunihi (Symantec), Worm.VBS.Dunihi.W (BitDefender)
Windows
Threat Type: Backdoor
Destructiveness: No
Encrypted: No
In the wild: Yes
OVERVIEW
This backdoor 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 drops copies of itself into all the removable drives connected to an affected system.
It executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.
TECHNICAL DETAILS
74,314 bytes
VBS
Yes
25 Aug 2015
Arrival Details
This backdoor 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 backdoor drops the following copies of itself into the affected system:
- %User Temp%\{Malware Filename}.vbs
(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.)
Autostart Technique
This backdoor adds the following registry entries to enable its automatic execution at every system startup:
HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{Malware Filename} = wscript.exe //B "%User Temp%\{Malware Filename}.vbs"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{Malware Filename} = wscript.exe //B "%User Temp%\{Malware Filename}.vbs"
Propagation
This backdoor drops copies of itself into all the removable drives connected to an affected system.
Backdoor Routine
This backdoor executes the following commands from a remote malicious user:
- Execute any file
- Update itself
- Uninstall itself
- Download file to the infected system
- Download file from specific website
- Upload file to C&C server
- List all available drives and send it to C&C server
- Enumerate the attributes of files and folders in a folder or set of folders given by the C&C server
- List all processes of the infected system and sends it to the C&C server
- Use command prompt
- Delete file or folder specified by c&c server
- Terminates running processes
- Sleep
It connects to the following websites to send and receive information:
- http://{BLOCKED}ckroot5.no-ip.org:77/is-ready
NOTES:
This backdoor drops shortcut files pointing to the copy of itself in removable drives. These dropped .LNK files use the names of the folders and files located on the said drives for their file names. It then sets the attributes of the original folders to System and Hidden to trick the user into clicking the .LNK files.
The .LNK files are detected as LNK_DUNIHI.SMIX.
SOLUTION
9.750
10.526.05
27 Jan 2014
10.527.00
28 Jan 2014
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
Remove the malware/grayware file dropped/downloaded by VBS_DUNIHI.AUM. (Note: Please skip this step if the threat(s) listed below have already been removed.)
- LNK_DUNIHI.SMIX
Step 4
Restart in Safe Mode
Step 5
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 Filename} = wscript.exe //B "%User Temp%\{Malware Filename}.vbs"
- {Malware Filename} = wscript.exe //B "%User Temp%\{Malware Filename}.vbs"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
- {Malware Filename} = wscript.exe //B "%User Temp%\{Malware Filename}.vbs"
- {Malware Filename} = wscript.exe //B "%User Temp%\{Malware Filename}.vbs"
Step 6
Restart in normal mode and scan your computer with your Trend Micro product for files detected as VBS_DUNIHI.AUM. 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.
Step 7
- Open a command prompt.
- For Windows 2000, Windows XP, and Windows Server 2003 users, click Start>Run. In the Search box, type CMD then press Enter.
- For Windows Vista, Windows 7, and Windows Server 2008 users, click Start, type CMD in the Search input field then press Enter.
- For Windows 8, Windows 8.1, and Windows Server 2012 users, right-click on the lower-left corner of the screen, click Command Prompt.
- In the CMD console, type the following:
ATTRIB [+R | -R] [+A | -A ] [+S | -S] [+H | -H] [+I | -I] [drive:][path][file name] [/S [/D] [/L]]
Where:
+ Sets an attribute.
- Clears an attribute
R Read-only file attribute
A Archive file attribute
S System file attribute
H Hidden file attribute
I Not content indexed file attribute
[drive:][path][filename]
Specifies a file or files for attrib to process
/S Processes matching files in the current folder and all subfolders.
/D Processes folders
/L Work on the attributes of the Symbolic Link versus the target of the Symbolic Link
Example:
To unhide all files and folders (including subfolders) in drive D:
ATTRIB –H D:\* /S /D
- Repeat Step 3 for folders and files in other drives or folders.
NOTES:
To unhide the infected files, please refer to the last step.
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