Analysis by: adel
 PLATFORM:

Windows 98, ME, NT, 2000, XP, Server 2003

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Trend Micro has flagged this backdoor as noteworthy due to the increased potential for damage, propagation, or both, that it possesses. Specifically, it is circulating and building armies (drones) especially in Vietnam and the APAC region.

To get a one-glance comprehensive view of the behavior of this Backdoor, refer to the Threat Diagram shown below.

This backdoor may be unknowingly downloaded by a user while visiting malicious websites.

  TECHNICAL DETAILS

File Size: Varies
File Type: PE
Memory Resident: Yes
Initial Samples Received Date: 31 Mar 2010
Payload: Drops files

Arrival Details

This backdoor may be unknowingly downloaded by a user while visiting malicious websites.

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
Microsoft Office quick launch = %Program Files%\Microsoft Office\OFFICE11\OSA.exe

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Microsoft Office quick launch = %Program Files%\Microsoft Office\OFFICE11\OSA.exe

Dropping Routine

This backdoor drops the following files:

  • %Program Files%\Adobe\AdobeUpdateManager.exe - detected by Trend Micro as TROJ_VB.ZAA
  • %Program Files%\Adobe\zf32.dll
  • %Program Files%\Windows Defender\MPClient.exe
  • %Program Files%\Windows Defender\MPSvc.exe
  • %Program Files%\Windows NT\Windows Update\wuauclt.exe
  • %Program Files%\Windows NT\Windows Update\zf32.dll
  • %System%\Setup\AdobeUpdateManager.exe - detected by Trend Micro as TROJ_VB.ZAA
  • %System%\Setup\jucheck.exe
  • %System%\Setup\MPClient.exe
  • %System%\Setup\MPSvc.exe
  • %System%\Setup\OSA.exe - also detected as BKDR_VBOT.A
  • %System%\Setup\wuauclt.exe - detected by Trend Micro as BKDR_VBBOT.AM
  • %System%\Setup\zf32.dll

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files.. %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

Other Details

Based on analysis of the codes, it has the following capabilities:

  • It drops a non malicious setup file called vpskeys, which is a Vietnamese keyboard driver. It then runs the file to avoid suspicion.

  SOLUTION

Minimum Scan Engine: 8.900
FIRST VSAPI PATTERN FILE: 6.964.01
FIRST VSAPI PATTERN DATE: 31 Mar 2010
VSAPI OPR PATTERN File: 6.965.00
VSAPI OPR PATTERN Date: 01 Apr 2010

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

Remove malware files dropped/downloaded by BKDR_VBOT.A

Step 3

Delete this registry value

[ Learn More ]

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
    • Microsoft Office quick launch = %Program Files%\Microsoft Office\OFFICE11\OSA.exe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Microsoft Office quick launch = %Program Files%\Microsoft Office\OFFICE11\OSA.exe

Step 4

Search and delete these files

[ Learn More ]
There may be some component files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %Program Files%\Adobe\zf32.dll
  • %Program Files%\Windows Defender\MPClient.exe
  • %Program Files%\Windows Defender\MPSvc.exe
  • %Program Files%\Windows NT\Windows Update\wuauclt.exe
  • %Program Files%\Windows NT\Windows Update\zf32.dll
  • %System%\Setup\jucheck.exe
  • %System%\Setup\MPClient.exe
  • %System%\Setup\MPSvc.exe
  • %System%\Setup\zf32.dll

Step 5

Scan your computer with your Trend Micro product to delete files detected as BKDR_VBOT.A. 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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