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WORM_MSIL.UF

October 09, 2012
 Analysis by: Erika Bianca Mendoza
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW


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

  TECHNICAL DETAILS

File Size:

245,760 bytes

File Type:

DLL

Memory Resident:

Yes

Initial Samples Received Date:

21 Nov 2011

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.

Autostart Technique

This worm registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\WamvSvc
ImagePath = "%System%\svchost.exe -k WamvSvc"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\WamvSvc\Parameters
ServiceDll = "{malware path and filename}"

Other System Modifications

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\SvcHost
WamvSvc = "WamvSvc Windows Information Vetfing"

Other Details

This worm connects to the following URL(s) to get the affected system's IP address:

  • www.ip138.com/ip2city.asp

It attempts to access the following websites to download files, which are possibly malicious:

  • {BLOCKED}t.{BLOCKED}4.info/donet.zip

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

8.624.04

FIRST VSAPI PATTERN DATE:

21 Nov 2011

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 NT\CurrentVersion\SvcHost
    • WamvSvc = "WamvSvc Windows Information Vetfing"

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_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • WamvSvc

Step 5

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