Analysis by: Michael Cabel
 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: No

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet

This Trojan may be downloaded by other malware/grayware from remote sites.

It connects to certain URLs. It may do this to remotely inform a malicious user of its installation. It may also do this to download possibly malicious files onto the computer, which puts the computer at a greater risk of infection by other threats. As of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size: Varies
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 05 Feb 2013
Payload: Downloads files

Arrival Details

This Trojan may be downloaded by the following malware/grayware from remote sites:

  • JAVA_EXPLOYT.NTW
  • JAVA_EXPLOYT.NEU

Installation

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

  • %Application Data%\skype.dat

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

It injects threads into the following normal process(es):

  • svchost.exe

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Winlogon
shell = "explorer.exe,%Application Data%\skype.dat"

Download Routine

This Trojan connects to the following malicious URLs:

  • http://{BLOCKED}r.ru/qnjtixjxqnjtixjxjkxjzhmpxx_gbcuakvrdmalau-ebexceihdkzo-zmdkpv-radatfstqu_plhc_pixorz-dmzv-yx.php

As of this writing, the said sites are inaccessible.

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 9.708.03
FIRST VSAPI PATTERN DATE: 05 Feb 2013
VSAPI OPR PATTERN File: 9.709.00
VSAPI OPR PATTERN Date: 06 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 the malware/grayware file that dropped/downloaded TROJ_RANSOM.NTW

Step 3

Restart in Safe Mode

[ Learn More ]

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 NT\CurrentVersion\Winlogon
    • shell = "explorer.exe,%Application Data%\skype.dat"

Step 5

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