Analysis by: Rhena Inocencio
ALIASES:

TrojanDownloader:Win32/Small.gen!AO (Microsoft), W32/Generic.worm!p2p (McAfee), a variant of Win32/VB.NTI trojan (ESET), Trojan.Win32.Generic.pak!cobra (Sunbelt)

 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.

It downloads a file from a certain URL then renames it before storing it in the affected system.

  TECHNICAL DETAILS

File Size: 131,072 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 21 Aug 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.

Other System Modifications

This Trojan modifies the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\helpsvc
ImagePath = "%System%\{random file name}.exe"

(Note: The default value data of the said registry entry is %System%\svchost.exe -k netsvcs.)

Process Termination

This Trojan terminates the following processes if found running in the affected system's memory:

  • 360tray.exe

Download Routine

This Trojan downloads files from the following URLs then renames them before storage in the affected system:

  • http://{BLOCKED}3.{BLOCKED}1.233.43:198/rc/Burning.jpg

It saves the files it downloads using the following names:

  • %System%\{random file name}.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.)

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}k.in:81/rc/xms/gx2.txt
  • http://{BLOCKED}2.{BLOCKED}5.245.172:88/rc/xms/gx2.txt
  • http://{BLOCKED}2.{BLOCKED}3.45.106:808/rc/xms/gx2.txt

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 9.338.03
FIRST VSAPI PATTERN DATE: 21 Aug 2012
VSAPI OPR PATTERN File: 9.339.00
VSAPI OPR PATTERN Date: 22 Aug 2012

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

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_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\helpsvc
    • From: ImagePath = "%System%\{random file name}.exe"
      To: ImagePath = "%System%\svchost.exe -k netsvcs"

Step 4

Search and delete this file

[ Learn More ]

There may be some component 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.
  • %System%\{random file name}.exe

Step 5

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