TROJ_AGENT.DVAB


 ALIASES:

PWS:Win32/Zbot.PK (Microsoft); Trojan Horse (Symantec); Worm.Win32.Pinit.gen (Kaspersky); Trojan.Generic.1808753 (FSecure)

 PLATFORM:

Windows 2000, XP, Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

  TECHNICAL DETAILS

File Size:

104,960 bytes

File Type:

EXE

Initial Samples Received Date:

06 Oct 2011

Arrival Details

This Trojan 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 Trojan drops the following copies of itself into the affected system:

  • %System%\ntos.exe

(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.)

It creates the following folders:

  • %System%\wsnpoem

(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 modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
userinit = "%System%\userinit.exe,%System%\ntos.exe,"

(Note: The default value data of the said registry entry is %System%\userinit.exe,.)

Other System Modifications

This Trojan deletes the following files:

  • %System%\ntos.exe
  • %System%\wsnpoem\video.dll.cla

(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.)

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Network
UID = "BRIAN-3D53544FA_00007985"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer
{F710FA10-2031-3106-8872-93A2B5C5C620} = {random values}

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Network
UID = "BRIAN-3D53544FA_0000BCD7"

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Network
UID = "BRIAN-3D53544FA_0000EE86"

Dropping Routine

This Trojan drops the following files:

  • %System%\wsnpoem\video.dll.cla

(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.)

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}r.com/z/cfg.bin

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.200

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

Identify and delete files detected as TROJ_AGENT.DVAB using either the Startup Disk or Recovery Console

[ Learn More ]

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Network
    • UID="BRIAN-3D53544FA_00007985"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer
    • {F710FA10-2031-3106-8872-93A2B5C5C620}={random values}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Network
    • UID="BRIAN-3D53544FA_0000BCD7"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Network
    • UID="BRIAN-3D53544FA_0000EE86"

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.exe,%System%\ntos.exe,"
      To: userinit=%System%\userinit.exe,

Step 5

Search and delete this folder

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result. %System%\wsnpoem

Step 6

Search and delete this file

[ 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%\wsnpoem\video.dll.cla

Step 7

Scan your computer with your Trend Micro product to delete files detected as TROJ_AGENT.DVAB. 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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