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Worm:Win32/Vobfus.gen!B


Worm:Win32/Vobfus.gen!B is a generic detection for obfuscated Visual Basic (VB) compiled malware that spreads via removable drives and downloads additional malware from remote servers.


What to do now

Manual removal is not recommended for this threat. To detect and remove this threat and other malicious software that may have been installed, run a full-system scan with an up-to-date antivirus product such as Microsoft Security Essentials, or the Microsoft Safety Scanner. For more information about using antivirus software, see http://www.microsoft.com/security/antivirus/av.aspx.

Threat behavior

Worm:Win32/Vobfus.gen!B is a generic detection for obfuscated Visual Basic (VB) compiled malware that spreads via removable drives and downloads additional malware from remote servers.
Installation
Worm:Win32/Vobfus.gen!B drops a copy of itself into the logged on user's profile directory as a random six character string, for example, "xealip.exe". Worm:Win32/Vobfus.gen!B modifies the registry to run the dropped copy at each Windows start as in the following example:
 
Adds value: "xealip"
With data: "%USERPROFILE%\xealip.exe"
To subkey: HKCU\Software\Microsoft\Windows\CurrentVersion\Run
Spreads via…
Removable drives
Worm:Win32/Vobfus.gen!B  enumerates removable drives and drops copies of the worm executable (for example, "xealip.exe" and "viuoqu.scr") under the root folder of each removable drive:
 
<drive:>\xealip.exe
<drive:>\viuoqu.scr
 
The worm then writes an autorun configuration file named "autorun.inf" pointing to the worm copy with ".exe" file extension. When the drive is accessed from a machine supporting the Autorun feature, the virus is launched automatically.
 
Worm:Win32/Vobfus.gen!B may also drop the following files on the removable drive:
 
z <two random characters>.lnk
z <two random characters>.dll
 
Remote drives
Worm:Win32/Vobfus.gen!B drops copies of the worm executable (for example, "xealip.exe" and "xealipx.exe") under the root folder of each writeable remote drive:
 
<drive:>\xealip.exe
<drive:>\xealipx.exe
 
The worm also creates shortcuts under the root directory on remote drives that have the same name as existing folders in the root directory, for example:
  • new folder.lnk
  • passwords.lnk
  • documents.lnk
  • pictures.lnk
  • music.lnk
  • video.lnk
  • subst.lnk
  • ..lnk
  • ...lnk
 
The shortcut links to the dropped worm executable with ".exe" file extension. Once the users opens the link, the worm copy will execute.
Payload
Modifies computer settings
Worm:Win32/Vobfus.gen!B modifies the following registry entries to prevent the user from changing how hidden files and folders are displayed in Windows Explorer:
 
Adds value: "ShowSuperHidden"
with data: "0"
To subkey: HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
 
Terminates processes and threads
Worm:Win32/Vobfus.gen!B prevents security software from terminating its processes by patching two Windows system APIs (TerminateProcess and TerminateThread).
 
Downloads and executes arbitrary files
Worm:Win32/Vobfus.gen!B tries to download additional files from a remote server under %UserProfile%; we have observed the worm contacting the following domain using TCP 8000:
  • theimageparlour.net
 
 
Analysis by Vincent Tiu

Symptoms

System changes
The following system changes may indicate the presence of this malware:
  • The presence of the following files in all removable drives:
    • z <two random characters>.lnk
    • z <two random characters>.dll
    • new folder.lnk
    • passwords.lnk
    • documents.lnk
    • pictures.lnk
    • music.lnk
    • video.lnk
    • subst.lnk
    • ..lnk
    • ...lnk

Prevention


Alert level: Severe
First detected by definition: 1.87.645.0
Latest detected by definition: 1.173.2181.0 and higher
First detected on: Jul 27, 2010
This entry was first published on: Jul 26, 2010
This entry was updated on: Apr 17, 2011

This threat is also detected as:
  • Worm:Win32/Vobfus.W (other)
  • TR/Dldr.VB.wps (Avira)
  • Trojan.Downloader.VB.WPO (BitDefender)
  • Win32/Vobfus.FH (CA)
  • Worm.Win32.VBNA.alpv (Kaspersky)
  • Downloader-CJX.gen.g (McAfee)
  • Mal/AutoRun-P (Sophos)
  • WORM_VBNA.SM (Trend Micro)
  • Worm.VBNA.Gen.3 (VirusBuster)