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WORM_YIMFOCA.AA

June 18, 2013
 ALIASES:

Worm:Win32/Yimfoca (Microsoft); BackDoor-EXI.gen.j (McAfee); Packed.Generic.329 (Symantec); IM-Worm.Win32.Yahos.ahu (Kaspersky); Trojan.Win32.Buzus.ga (v) (Sunbelt); Trojan horse Dropper.Generic3.AKIR (AVG)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • 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.

  TECHNICAL DETAILS

File Size:

157,184 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

08 Jun 2013

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:

  • %Windows%\nvsvc32.exp

(Note: %Windows% is the Windows folder, which is usually C:\Windows.)

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
NVIDIA driver monitor = "%Windows%\nvsvc32.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
NVIDIA driver monitor = "%Windows%\nvsvc32.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Terminal Server\
Install\Software\Microsoft\
Windows\CurrentVersion\Run
NVIDIA driver monitor = "%Windows%\nvsvc32.exe"

Other System Modifications

This worm deletes the following files:

  • %System Root%\mdlu.dl
  • %System Root%\mtdlh.dl
  • %Windows%\nvsvc32.exp
  • %Windows%\mdlu.dl
  • %Windows%\mtdlh.dl

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %Windows% is the Windows folder, which is usually C:\Windows.)

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
{malware path and file name} = "{malware path and file name}:*:enabled:nvidia driver monitor"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
{malware path and file name} = "%Windows%\nvsvc32.exe:*:Enabled:NVIDIA driver monitor"

Dropping Routine

This worm drops the following files:

  • %Windows%\nvsvc32.exe

(Note: %Windows% is the Windows folder, which is usually C:\Windows.)

Other Details

This worm connects to the following possibly malicious URL:

  • http://{BLOCKED}5.106.162/index.php

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.300

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

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
    • NVIDIA driver monitor = "%Windows%\nvsvc32.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • NVIDIA driver monitor = "%Windows%\nvsvc32.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Terminal Server\Install\Software\Microsoft\Windows\CurrentVersion\Run
    • NVIDIA driver monitor = "%Windows%\nvsvc32.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • {malware path and file name} = "{malware path and file name}:*:enabled:nvidia driver monitor"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • {malware path and file name} = "%Windows%\nvsvc32.exe:*:Enabled:NVIDIA driver monitor"

Step 4

Search and delete this file

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %Windows%\nvsvc32.exe

Step 5

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

Step 6

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %System Root%\mdlu.dl
  • %System Root%\mtdlh.dl
  • %Windows%\nvsvc32.exp
  • %Windows%\mdlu.dl
  • %Windows%\mtdlh.dl


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