Analysis by: JessaD
ALIASES:

Worm:Win32/Vobfus.gen!E (Microsoft), Downloader-CJX.gen.o (Mcafee)

 PLATFORM:

Windows 2000, XP, Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

This worm arrives via removable drives. It may be downloaded by other malware/grayware/spyware from remote sites. It may be dropped by other malware.

It drops copies of itself into all the removable drives connected to an affected system. 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: 237,568 bytes
File Type: PE
Memory Resident: Yes
Initial Samples Received Date: 22 Jan 2011

Arrival Details

This worm arrives via removable drives.

It may be downloaded by other malware/grayware/spyware from remote sites.

It may be dropped by other malware.

Installation

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

  • %User Profile%\{random name}.exe

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random name} = %User Profile%\{random name}.exe /p

Other System Modifications

This worm modifies the following registry entries to hide files with Hidden attributes:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
ShowSuperHidden = 0

(Note: The default value data of the said registry entry is 1.)

Propagation

This worm drops copies of itself into all the removable drives connected to an affected system.

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:

{garbage}
[AUtORUn]
{garbage}
ACTIOn=View Files
{garbage}
shELlEXecUTE={random name}.EXe
{garbage}
ICOn=%systeMroot%\systEM32\sheLL32.Dll,4
{garbage}
USEautOplay=1
{garbage}

Dropping Routine

This worm sets the attributes of its dropped file(s) to the following:

  • Hidden
  • System
  • Read Only

Other Details

This worm does the following:

  • Drops .LNK files that reference a copy of itself in removable drives. These dropped files use the names of the folders located on the said drives for their filenames. It then hides the original folders to further fool the users. In addition, it also uses the following names:
    • Documents.lnk
    • Music.lnk
    • New Folder.lnk
    • Passwords.lnk
    • Pictures.lnk
    • Video.lnk
  • Attempts to resolve the following host names:
    • {BLOCKED}ayer1253.com
    • {BLOCKED}deoall.net
    • {BLOCKED}diashares.org

  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

Scan your computer with your Trend Micro product and note files detected as WORM_VBNA.SMTA

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

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.

 HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
{random name} = %User Profile%\{random name}.exe /p

Step 5

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.

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
ShowSuperHidden = 0

1

Step 6

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. {Removable Drive}\Documents.lnk
{Removable Drive}\Music.lnk
{Removable Drive}\New Folder.lnk
{Removable Drive}\Passwords.lnk
{Removable Drive}\Pictures.lnk
{Removable Drive}\Video.lnk
{Removable Drive}\{folder name}.lnk

Step 7

Search and delete AUTORUN.INF files created by WORM_VBNA.SMTA that contain these strings

[ Learn More ]
{garbage}
[AUtORUn]
{garbage}
ACTIOn=View Files
{garbage}
shELlEXecUTE={random name}.EXe
{garbage}
ICOn=%systeMroot%\systEM32\sheLL32.Dll,4
{garbage}
USEautOplay=1
{garbage}

Step 8

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