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TROJ_VB.ZAA

April 01, 2010
 Analysis by:
 PLATFORM:

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

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


Trend Micro has flagged this Trojan as noteworthy due to the increased potential for damage, propagation, or both, that it possesses. This Trojan is related to another noteworthy entry BKDR_VBOT.A



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



This Trojan may be dropped by other malware.



It adds registry entries to enable its automatic execution at every system startup.



It listens on ports. It executes commands from a remote malicious user, effectively compromising the affected system.



It accesses websites to download files. This action allows this malware to possibly add other malware on the affected computer.



  TECHNICAL DETAILS

File Size:

237568 bytes

Memory Resident:

Yes

Initial Samples Received Date:

06 Jan 2010


Arrival Details


This Trojan may be dropped by the following malware:

  • BKDR_VBOT.A



Installation


This Trojan drops the following files:

  • %System%\MSCONFIG32.SYS

(Note: %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.)



Autostart Technique


This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Winlogon
Userinit =  

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Adobe Update Manager = {malware path and file name}

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
Adobe Update Manager = {malware path and file name}



Backdoor Routine


This Trojan listens on the following port(s):

  • TCP port 8585


It executes the following commands from a remote malicious user:

  • {BLOCKED}.ath.cx
  • {BLOCKED}s.ath.cx



Download Routine


This Trojan accesses websites to download the following files:

  • msimsg32.vxd
  • ntconf32.dll
  • ntsys32.vxd



Other Details


This Trojan connects to the following possibly malicious URL:

  • {BLOCKED}.{BLOCKED}ix.com
  • {BLOCKED}r.{BLOCKED}.org


  SOLUTION

Minimum Scan Engine:

8.900

VSAPI OPR PATTERN File:

6.793.00

VSAPI OPR PATTERN Date:

21 Jan 2010


Step 1


For Windows ME and XP 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 TROJ_VB.ZAA
    • 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 NT\CurrentVersion\Winlogon
    • Userinit =  
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Adobe Update Manager = {malware path and file name}
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
    • Adobe Update Manager = {malware path and file name}


Step 4


Restore this modified 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_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon
  • From: Userinit = %System%\userinit,{malware path and filename}

  • To: Userinit = %System%\userinit.exe,


Step 5


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.
  • %System%\MSCONFIG32.SYS


Step 6


Scan your computer with your Trend Micro product to delete files detected as TROJ_VB.ZAA 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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