Analysis by: Sabrina Lei Sioting
ALIASES:

Trojan:Win32/Vundo.IX (Microsoft); Trojan.Win32.Monderd.gen (Kaspersky); Vundo (McAfee); Troj/Virtum-Gen (Sophos); Trojan.Vundo.Gen.4 (FSecure); Trojan.Win32.Monder.gen.1 (Sunbelt); Trojan.Win32.Monderd (Ikarus)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Dropped by other malware, Downloaded from the Internet

This Trojan connects to URLs to download malicious files. It also drops malicious files onto the affected system.

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.

It lowers the security setting of Internet Explorer.

  TECHNICAL DETAILS

File Size: 238,592 bytes
File Type: DLL
Memory Resident: Yes
Initial Samples Received Date: 22 Jun 2009
Payload: Downloads files, Drops files, Connects to URLs/IPs, Compromises system security

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 non-malicious file:

  • %System%\bb911232-.txt

(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 injects itself into the following processes running in the affected system's memory:

  • explorer.exe

Autostart Technique

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

HKEY_CLASSES_ROOT\CLSID\{random CLSID}\
InprocServer32
{default} = "{malware path}\{malware name}.dll"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{random CLSID}\InprocServer32
{default} = "{malware path}\{malware name}.dll"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{Random Name} = "Rundll32.exe {malware path}\{malware name}.dll,s"

It registers itself as a BHO to ensure its automatic execution every time Internet Explorer is used by adding the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects\{random CLSID}

Other System Modifications

This Trojan adds the following registry entries as part of its installation routine:

HKEY_CLASSES_ROOT\CLSID\{random CLSID}\
InprocServer32
ThreadingModel = "Both"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{random CLSID}\InprocServer32
ThreadingModel = "Both"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Windows
LoadAppInit_DLLs = "1"

It modifies the following registry key(s)/entry(ies) as part of its installation routine:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wuauserv
Start = "4"

(Note: The default value data of the said registry entry is 2.)

It adds the following registry keys as part of its installation routine:

HKEY_CLASSES_ROOT\CLSID\{random CLSID}

HKEY_CLASSES_ROOT\CLSID\{random CLSID}\
InprocServer32

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{random CLSID}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{random CLSID}\InprocServer32

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
{random characters}

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
FCOVM

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
RemoveRP

Web Browser Home Page and Search Page Modification

This Trojan lowers the security setting of Internet Explorer.

Dropping Routine

This Trojan drops the following files:

  • {malware path}\{malware name}.ini - detected as Mal_VundoG
  • {malware path}\{malware name}.ini2 - detected as Mal_VundoG

Download Routine

This Trojan connects to the following website(s) to download and execute a malicious file:

  • http://{BLOCKED}6.138/32/32.dll?setid=an2g&affid={data}&uid=&rid=vm571&guid={guid} - detected by Trend Micro as TROJ_VUNDO.JWE
  • http://{BLOCKED}9.55/i.exe?setid=an2g&affid={data}&uid=&rid=vm571&guid={guid} - detected as TROJ_DLOADR.ARP

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 6.214.03
FIRST VSAPI PATTERN DATE: 22 Jun 2009
VSAPI OPR PATTERN File: 6.215.00
VSAPI OPR PATTERN Date: 23 Jun 2009

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

Restart in Safe Mode

[ Learn More ]

Step 3

Remove malware files dropped/downloaded by TROJ_VUNDO.KQF

    Mal_VundoG
    TROJ_VUNDO.JWE
    TROJ_DLOADR.ARP

Step 4

Delete this registry key

[ 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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

 
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft
    • {random characters}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft
    • FCOVM
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft
    • RemoveRP

Step 5

Delete the created random CLSID key

[ 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.

Step 6

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\CurrentVersion\Run
    • {Random Name} = "Rundll32.exe {malware path}\{malware name}.dll,s"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows
    • LoadAppInit_DLLs = "1"

Step 7

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\SYSTEM\CurrentControlSet\Services\wuauserv
    • From: Start = "4"
      To: Start = 2

Step 8

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%\bb911232-.txt

Step 9

Scan your computer with your Trend Micro product to delete files detected as TROJ_VUNDO.KQF. 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.


Did this description help? Tell us how we did.

Related Malware