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TROJ_HIDFILE.INF

October 08, 2012
 Analysis by: Roland Marco Dela Paz
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes


  TECHNICAL DETAILS

File Size:

195,763 bytes

File Type:

PE

Memory Resident:

Yes

Initial Samples Received Date:

21 Mar 2011

Installation

This Trojan drops the following files:

  • %User Temp%\Temp\notpad.exe - also detected as TROJ_HIDFILE.INF
  • %User Temp%\Temp\RGZ DECODER.EXE - non-malicious file

(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.)

It creates the following folders:

  • %User Temp%\Temp

(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.)

NOTES:

It searches for executable files (.EXE) on the affected system. Once a file is found, it hides the file by removing the ".exe" extension on its file name and by setting its attribute to Hidden. It then drop a copy of itself using the file name of the Hidden file. This routine serves as an autostart mechanism of this malware.

The dropped copies also contain a code that executes the original files in order to avoid users from suspecting system infection.

  SOLUTION

Minimum Scan Engine:

8.900

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

Scan your computer with your Trend Micro product to delete files detected as TROJ_HIDFILE.INF. 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 3

Search and delete these files

[ 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.
  • %User Temp%\Temp

NOTES:

Restore Hidden Files

To restore the modified files:

  1. Open Command prompt. Click Start>Run, type cmd, then press Enter.
  2. Type the following then press enter:

    {modified file path}
    {modified file path}:\attrib -s -h -r {file name}
    {modified file path}:\ ren {file name} {file name}.exe
  3. Close command prompt.


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