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TROJ_DROPPR.VTG

June 23, 2013
 ALIASES:

TrojanDropper:Win32/Malf.gen (Microsoft); [0005df34.EXE]:Dropper-FAC!69F32B85F1DE (McAfee); PAK:UPX (Kaspersky); BehavesLike.Win32.Malware.bsf (vs) (Sunbelt); MemScan:Trojan.Generic.6286669 (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Trojan 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:

334,336 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

18 Apr 2012

Arrival Details

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

  • %System Root%\Documents and Settings.exe
  • %Windows%.exe

(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 creates the following folders:

  • %Program Files%\Tencent

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).)

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Tbsolute

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\NWCWorkstation\Parameters

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Tbsolute
values = "{random values}"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\NWCWorkstation\Parameters
ServiceDll = "%SystemRoot%\system32\nwcwks.dll"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Tbsolute
guid = "3E4061B5-B985-45E4-B20B-39E816490990"

Dropping Routine

This Trojan drops the following files:

  • %Program Files%\Tencent\calc.exe
  • %System%\nwcwks.dll

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).. %System% is the Windows system folder, which is usually C:\Windows\System32.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.200

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

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\SOFTWARE\Microsoft
    • Tbsolute
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\NWCWorkstation
    • Parameters

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\Tbsolute
    • values = "{random values}"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\NWCWorkstation\Parameters
    • ServiceDll = "%SystemRoot%\system32\nwcwks.dll"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Tbsolute
    • guid = "3E4061B5-B985-45E4-B20B-39E816490990"

Step 4

Search and delete these components

[ Learn More ]
There may be some components 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.
  • %Program Files%\Tencent\calc.exe
  • %System%\nwcwks.dll

Step 5

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%\Tencent

Step 6

Scan your computer with your Trend Micro product to delete files detected as TROJ_DROPPR.VTG. 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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