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WORM_FAILNUM.A

January 07, 2015
 Analysis by: Michelle Morales
 ALIASES:

IM-Worm.Win32.Agent.pt (Kaspersky)

 PLATFORM:

Windows

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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

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:

80,896 bytes

File Type:

EXE

Memory Resident:

Yes

Arrival Details

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

  • %User Temp%\vshost32.exe

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

Autostart Technique

This worm 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,%User Temp%\vshost32.exe"

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

Other System Modifications

This worm adds the following registry entries:

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
BuildID = "d3adc0de"

Propagation

This worm drops the following copy(ies) of itself in all removable drives:

  • {removable drive}\vshost.exe

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

Other Details

This worm connects to the following possibly malicious URL:

  • http://fubar.{BLOCKED}ocks.cn:80/check.php?p1=12345&p2=USA
  • http://win.{BLOCKED}ngcenter-org.com
  • http://ns.{BLOCKED}o-net.com

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

6.632.02

FIRST VSAPI PATTERN DATE:

17 Nov 2009

VSAPI OPR PATTERN File:

6.633.00

VSAPI OPR PATTERN Date:

17 Nov 2009

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

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,%User Temp%\vshost32.exe"
      To: Userinit = %System%\userinit.exe

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.

  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • BuildID = "d3adc0de"

Step 5

Search and delete AUTORUN.INF files created by WORM_FAILNUM.A that contain these strings

[ Learn More ]
[autorun] icon=%systemroot%\SYSTEM32\SHELL32.Dll,4   Action=Open folder to view files   ShellExecute=vshost.exe 

Step 6

Scan your computer with your Trend Micro product to delete files detected as WORM_FAILNUM.A. 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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