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TROJ_RANSOM.BOV

February 23, 2012
 Analysis by: Roland Marco Dela Paz
 ALIASES:

Trojan:Win32/Ransom.FL (Microsoft)

 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

  OVERVIEW

Infection Channel:

Downloaded from the Internet

This ransomware was spread via a compromised website of a well-known confectionery company based in France, Laduree.

To get a one-glance comprehensive view of the behavior of this Trojan, refer to the Threat Diagram shown below.

Upon execution, this Trojan connects to a certain site to get the IP address, geographical location, city, and Internet Service Provider (ISP) of the affected system. It then blocks the desktop of the user and displays an image. The image accuses the user of violating the laws of France for several fabricated offenses. It then demands users to pay a fine via Ukash or Paysafecard voucher.

This Trojan may be unknowingly downloaded by a user while visiting malicious websites.

  TECHNICAL DETAILS

File Size:

Varies

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

21 Feb 2012

Payload:

Displays graphics/image

Arrival Details

This Trojan may be unknowingly downloaded by a user while visiting malicious websites.

Installation

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

  • %Windows%\explorer.exe
  • %System%\explorer.exe

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

Process Termination

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

  • taskmgr.exe
  • procexp.exe

NOTES:

Upon execution, it connects to the following site to get the IP address, geographical location, city, and Internet Service Provider (ISP) of the affected system:

  • http://{BLOCKED}ls.{BLOCKED}location.com/ib2/

It then blocks the desktop of the user and displays the following image:

The image above accuses the user of violating the laws of France for several fabricated offenses. It then demands users to pay a fine via Ukash or Paysafecard voucher.

It reports system infection to any of the following sites:

  • {BLOCKED}wuusaf.com
  • {BLOCKED}rpeprt.ru
  • {BLOCKED}sxppsy.com
It sends the following HTTP request to the said sites:
  • http://{domain}/{BLOCKED}e.php?cmd=ping&botnet={parameter}&userid={encoded user ID}&os={encoded operating system version}

It saves the original explorer.exe file as follows:

  • %Windows%\twexx32.dll

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

8.792.08

FIRST VSAPI PATTERN DATE:

21 Feb 2012

VSAPI OPR PATTERN File:

8.793.00

VSAPI OPR PATTERN Date:

22 Feb 2012

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

Scan your computer with your Trend Micro product to delete files detected as TROJ_RANSOM.BOV. 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.

NOTES:

Do as Step 2:

To identify and delete the malware/grayware file:

  1. Insert your Windows Installation CD in your CD-rom.
  2. Press the restart button of your computer.
  3. When prompted, press any key to boot from the CD.
  4. When prompted on the Main Menu, type r to enter the recovery console.
    (Note: On Windows 2000, after pressing r, type c to choose the Recovery Console in the repair options screen.)
  5. When prompted, type your administrator password to log on.
  6. Once logged in, type the drive that contains Windows in the command prompt that appears, then press Enter.
  7. Type the following, then press Enter:

    del %Windows%\explorer.exe
    del %System%\explorer.exe
    copy %Windows%\twexx32.dll %Windows%\explorer.exe
    del %Windows%\twexx32.dll

  8. Type exit to restart the system normally.


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