Analysis by: Michael Cabel
 PLATFORM:

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

 OVERALL RISK RATING:
 REPORTED INFECTION:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This worm modifies registry entries to hide files with System and Read-only attributes.

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

It deletes itself after execution.

  TECHNICAL DETAILS

File Size: 90,183 bytes
File Type: PE
Memory Resident: Yes
Initial Samples Received Date: 05 Aug 2008

Installation

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

  • %System%\mmvo.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.)

It drops the following file(s)/component(s):

  • %System%\mmvo0.dll - detected as TROJ_INHOO.Z

(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.)

Other System Modifications

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

HKEY_CLASSES_ROOT\CLSID\MADOWN
=

It modifies the following registry entries to hide files with System and Read-only attributes:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = 2

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

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

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced\Folder\Hidden\
SHOWALL
CheckedValue = 0

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

Propagation

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

  • xt9.com

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 Characters}
[AutoRun]
;{Garbage Characters}
open=xt9.com
;{Garbage Characters}
shell\open\Command=xt9.com
;{Garbage Characters}
shell\open\Default=1
;{Garbage Characters}
shell\explore\Command=xt9.com
;{Garbage Characters}

Other Details

This worm deletes itself after execution.

  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_LINEAGE.NP

    TROJ_INHOO.Z

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.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • mmva = %System%\mmvo.exe

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.

 
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: Hidden = 2
      To: 1
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: ShowSuperHidden = 0
      To: 1
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Folder\Hidden\SHOWALL
    • From: CheckedValue = 0
      To: 1

Step 6

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_CLASSES_ROOT\CLSID
    • MADOWN

Step 7

Scan your computer with your Trend Micro product to delete files detected as WORM_LINEAGE.NP. 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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