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TROJ_DLOADR.YUGV

April 08, 2014
 Analysis by: Mark Joseph Manahan
 ALIASES:

[6.nsis]:Generic Downloader.g (McAfee) ,Trojan.Win32.Generic!BT (Sunbelt)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • 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:

323,974 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

02 Apr 2014

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 creates the following folders:

  • %System%\dfrg
  • %System%\dfrg\cpu

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

Autostart Technique

This Trojan 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\winnetdns
ImagePath = "%System%\dfrg\svc.exe"

It registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\winnetdns

Other System Modifications

This Trojan creates the following registry entry(ies) to bypass Windows Firewall:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%System%\dfrg\cpu\cpu.exe = "%System%\dfrg\cpu\cpu.exe:*:Enabled:%System%\dfrg\cpu\cpu.exe (in)"

Download Routine

This Trojan saves the files it downloads using the following names:

  • %System%\dfrg\cpu\cpu.exe
  • %System%\dfrg\cpu\libcurl-4.dll
  • %System%\dfrg\cpu\pthreadGC2.dll
  • %System%\dfrg\mst.exe
  • %System%\dfrg\stub.exe
  • %System%\dfrg\svc.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

Other Details

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

  • http://{BLOCKED}tfosterhumbertlombo.mrface.com/cpu_32.zip

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

10.702.09

FIRST VSAPI PATTERN DATE:

02 Apr 2014

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 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\SYSTEM\CurrentControlSet\Services
    • winnetdns

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_LOCAL_MACHINE\System\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • %System%\dfrg\cpu\cpu.exe = "%System%\dfrg\cpu\cpu.exe:*:Enabled:%System%\dfrg\cpu\cpu.exe (in)"

Step 5

Search and delete these folders

[ 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.
  • %System%\dfrg

Step 6

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