Analysis by: JasperM
 PLATFORM:

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

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This worm arrives by connecting affected removable drives to a system. It may be dropped by other malware. It may be unknowingly downloaded by a user while visiting malicious websites.

It drops copies of itself in all removable drives. It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

  TECHNICAL DETAILS

File Size: 131,072 bytes
File Type: PE
Memory Resident: Yes
Initial Samples Received Date: 29 Jul 2010
Payload: Drops files

Arrival Details

This worm arrives by connecting affected removable drives to a system.

It may be dropped by other malware.

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

Installation

This worm drops the following files:

  • %User Profile%\{random}.EXE - copy of itself

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

Autostart Technique

This worm creates the following registry entries to enable automatic execution of dropped component at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{malware name} = %User Profile%\{malware name}.EXE

Propagation

This worm drops copies of itself in all removable drives.

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

The said .INF file contains the following strings:

[aUtOrUN]
ACTioN=Open folder to view files
sHeLlexECuTe=tiAZEh.exe
iCoN=%systEmRoot%\syStem32\ShElL32.dll,4
uSEAutoPLay=1

Dropping Routine

This worm drops the following files:

  • LNK files, which are detected as LNK_STUXNET.SM

Other Details

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

  • The dropped LNK files exploit the vulnerability found in this report: http://www.microsoft.com/technet/security/advisory/2286198.mspx
  • It also drops non-malicious LNK files to removable drives which are shortcuts to the malware file.
  • It also drops the following files in all removable drives which is executed by the dropped LNK files: ert.dll - detected as TROJ_ZAPCHAST.LA

  SOLUTION

Minimum Scan Engine: 8.900

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 WORM_VBNA.RL

    LNK_STUXNET.SM
    TROJ_ZAPCHAST.LA

Step 3

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. DATA_GENERIC
Note: To do a search for the following files, right-click Start then click Search... or Find..., depending on the version of Windows you are running. For each file to be deleted, type its file name in the Named input box. In the Look In drop-down list, select My Computer, then press Enter.
  • Once located, select the file then press SHIFT+DELETE to permanently delete the file.
  • Repeat the said steps for all files listed.

    • Step 4

    Delete the registry entry with an unknown data 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.

    DATA_GENERIC_KEY
  • In the right panel, locate and delete the entry or entries whose data value is the malware path and file name of the file(s) detected earlier.
  • Close Registry Editor.

    • Step 5

    Scan your computer with your Trend Micro product to delete files detected as WORM_VBNA.RL. 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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