WORM_AUTORUN.YZB

October 08, 2012
 Analysis by: Michael Cabel
 ALIASES:

Microsoft: VirTool:INF/Autorun.gen!A;

 PLATFORM:

Windows 2000, XP, Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Copies itself in all available physical drives, Propagates via removable drives

It drops component files detected as BKDR_IRCFLOOD.CN and TROJ_LAMEWAR.VTG.

This worm arrives as a component bundled with malware/grayware packages. It may be unknowingly downloaded by a user while visiting malicious websites.

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

It executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.

  TECHNICAL DETAILS

File Size:

1,964,050 bytes

File Type:

PE

Memory Resident:

Yes

Initial Samples Received Date:

02 Sep 2010

Payload:

Drops files

Arrival Details

This worm arrives as a component bundled with malware/grayware packages.

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

Installation

This worm drops the following component file(s):

  • %Program Files%\MSNM\spoolvsc.exe - detected as BKDR_IRCFLOOD.CN
  • %Program Files%\MSNM\irsss.hlp - detected as TROJ_LAMEWAR.VTG

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files.)

It drops the following non-malicious files:

  • %Program Files%\MSNM\uninstall.uni
  • %Program Files%\MSNM\aliases.ini
  • %Program Files%\MSNM\Beclickz.dll
  • %Program Files%\MSNM\imds.hlp
  • %Program Files%\MSNM\ionfgs.hlp
  • %Program Files%\MSNM\mirc.ini
  • %Program Files%\MSNM\Refix.ocx
  • %Program Files%\MSNM\sysingb32.dll
  • %Program Files%\MSNM\systemac.dll
  • %Program Files%\MSNM\winregs.ocx

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files.)

It drops the following copies of itself into the affected system:

  • %Windows%\J_Y.exe
  • %Windows%\J-Y.exe
  • %System%\J_Y.exe

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.. %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 creates the following folders:

  • %Program Files%\MSNM
  • %Program Files%\MSNM\download

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files.)

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
J_Y = "%Windows%\J_Y.exe"

Other System Modifications

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

HKEY_LOCAL_MACHINE\SOFTWARE\instyler

Propagation

This worm drops the following copies of itself in all physical and removable drives:

  • J_Y.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=J_Y.exe
shell\open\Command=J_Y.exe
shell\open\Default=1
shell\explore\Command=J_Y.exe

Dropping Routine

This worm executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.

  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_AUTORUN.YZB

    BKDR_IRCFLOOD.CN
    TROJ_LAMEWAR.VTG

Step 3

Terminate a process file/s detected as WORM_AUTORUN.YZB

[ Learn More ]

*Note: If the detected file/s is/are not displayed in theWindows Task Manager, continue doing the next steps.

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\CurrentVersion\Run
    • J_Y = %Windows%\J_Y.exe

Step 5

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
    • instyler

Step 6

Search and delete this folder

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.   %Program Files%\MSNM

Step 7

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

[ Learn More ]
[AutoRun]
open=J_Y.exe
shell\open\Command=J_Y.exe
shell\open\Default=1
shell\explore\Command=J_Y.exe

Step 8

Scan your computer with your Trend Micro product to delete files detected as WORM_AUTORUN.YZB. 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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