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WORM_AUTORUN.BGW

October 08, 2012
 Analysis by: Roland Marco Dela Paz
 ALIASES:

Symantec : W32.SillyFDC; Microsoft : Worm:Win32/Autorun.CY

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

It attempts to access certain websites. However, the websites are inaccessible as of this writing.

  TECHNICAL DETAILS

File Size:

46,080 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

01 Feb 2011

Installation

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

  • %System%\dsncb.exe

(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.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
dxncb = %System%\dsncb.exe

Other System Modifications

This worm adds the following registry keys:

HKEY_CURRENT_USER\Software\{random}

HKEY_CURRENT_USER\Software\Microsoft\
DsNiu

Propagation

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

  • dsncb.exe

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]
Open=dsncb.exe
Shell\Open=´ò¿ª(&O)
Shell\Open\Command=dsncb.exe
Shell\Open\Default=1
Shell\Explore=×ÊÔ´¹ÜÀíÆ÷(&X)
Shell\Explore\Command=dsncb.exe

Other Details

This worm attempts to access certain websites. However, the websites are inaccessible as of this writing.

It connects to the following possibly malicious URL:

  • http://user.{BLOCKED}2.77169.net//hy1211/List.txt

  SOLUTION

Minimum Scan Engine:

8.900

VSAPI PATTERN File:

7.806.01

VSAPI PATTERN Date:

01 Feb 2011

VSAPI PATTERN Date:

2/1/2011 12:00:00 AM

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

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
    • dxncb = %System%\dsncb.exe

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.

  • In HKEY_CURRENT_USER\Software
    • qmnmc
  • In HKEY_CURRENT_USER\Software\Microsoft\
    • DsNiu

Step 5

Search and delete AUTORUN.INF files created by WORM_AUTORUN.BGW that contain these strings

[ Learn More ]
[autorun]
Open=dsncb.exe
Shell\Open=´ò¿ª(&O)
Shell\Open\Command=dsncb.exe
Shell\Open\Default=1
Shell\Explore=×ÊÔ´¹ÜÀíÆ÷(&X)
Shell\Explore\Command=dsncb.exe

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_AUTORUN.BGW. 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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