Analysis by: Jaime Benigno Reyes

 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:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Dropped by other malware

This Trojan may be dropped by other malware.

  TECHNICAL DETAILS

File Size: 24,576 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 22 Feb 2013
Payload: Connects to URLs/IPs, Downloads files

Arrival Details

This Trojan may be dropped by the following malware:

  • TROJ_PIDIEF.EVF

Installation

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

  • %System Root%\Users\Public\Music\AcroRd32Info.exe (Windows Vista and 7 only)
  • %System Root%\Documents and Settings\All Users\Documents\My Music\AcroRd32Info.exe (versions other than Windows Vista and 7)

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

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
ShStatEXE = "%System Root%\Users\Public\Music\AcroRd32Info.exe" (Windows Vista and 7 only)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
ShStatEXE = "%System Root%\Documents and Settings\All Users\Documents\My Music\AcroRd32Info.exe" (versions other than Windows Vista and 7)

Download Routine

This Trojan connects to the following website(s) to download and execute a malicious file:

  • http://{BLOCKED}s.{BLOCKED}n.dynssl.com/{variable}.gif

It saves the files it downloads using the following names:

  • %User Temp%\{random}.exe

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

NOTES:

It only connects to the following URL every Tuesday between 8:00 AM and 6:59 PM:

  • http://{BLOCKED}s.{BLOCKED}n.dynssl.com/{variable}.gif

This Trojan continuously connects to the following non-malicious URL(s) to trick users into thinking it is legitimate software:

  • http://www.shounkaku.co.jp/space/{variable}.gif

The term variable depends on the host name and system language ID of the computer.

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 9.744.04
FIRST VSAPI PATTERN DATE: 22 Feb 2013
VSAPI OPR PATTERN File: 9.745.00
VSAPI OPR PATTERN Date: 22 Feb 2013

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

Remove malware/grayware files that dropped/downloaded TROJ_AGENT.EVF

     
    • TROJ_PIDIEF.EVF

Step 3

Identify and terminate files detected as TROJ_AGENT.EVF

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • ShStatEXE = "%System Root%\Users\Public\Music\AcroRd32Info.exe" (Windows Vista and 7 only)
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • ShStatEXE = "%System Root%\Documents and Settings\All Users\Documents\My Music\AcroRd32Info.exe" (versions other than Windows Vista and 7)

Step 5

Search and delete these files

[ 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.
  • %User Temp%\{random}.exe

Step 6

Scan your computer with your Trend Micro product to delete files detected as TROJ_AGENT.EVF. 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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