BKDR_DUSVEXT.B

November 03, 2012
 Analysis by: Mark Joseph Manahan
 ALIASES:

Trojan:Win32/Dusvext.A (Microsoft), PWS-Zbot.gen.ajw (McAfee), Win32/Vnfraye.A trojan (Eset), Trojan.Gen (Symantec)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet

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

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

File Size:

147,968 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

02 Nov 2012

Payload:

Compromises system security, Connects to URLs/IPs

Arrival Details

This backdoor 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:

  • %System Root%\svstem32.exe

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • VN_MUTEX16

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
svstem32 = %System Root%\svstem32.exe

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Send message box
  • Execute arbitrary commands
  • Download and execute arbitrary files
  • Get the process list
  • Get the modules list
  • Capture keystrokes
  • Retrieve the keylogger logs
  • Read file contents and retrieve it
  • Uninstall and terminate itself
  • Httpflood
  • Remote shell
  • Visit any webpage
  • Update itself
  • Steal informations (Hardware UID, LAN Ip Address, Computer Name, Country, Idle Time, Country Code)
  • It may perform additional plugins (Webcam Capture, Desktop Capture, Sound Capture, etc.)

It connects to the following websites to send and receive information:

  • http://www.{BLOCKED}t-mr.com/images/.vr/tasks.php?uid={UID}
  • http://www.{BLOCKED}t-mr.com/images/.vr/adduser.php?uid=UID}
  • http://www.{BLOCKED}t-mr.com/VertexNet/

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

9.502.01

FIRST VSAPI PATTERN DATE:

02 Nov 2012

VSAPI OPR PATTERN File:

9.503.00

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 terminate files detected as BKDR_DUSVEXT.B

[ Learn More ]
  1. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  2. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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
    • svstem32 = %System Root%\svstem32.exe

Step 4

Scan your computer with your Trend Micro product to delete files detected as BKDR_DUSVEXT.B 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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