Analysis by: Anthony Joe Melgarejo

ALIASES:

Trojan:Win32/Bumat!rts (Microsoft), Trojan.Ransomlock.P (Symantec), TR/Jorik.Androm.pgr (Antivir), Trojan-Ransom.Win32.Blocker (Ikarus), Win32/Trustezeb.C trojan (ESET)

 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: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet, Dropped by other malware

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It executes commands from a remote malicious user, effectively compromising the affected system.

  TECHNICAL DETAILS

File Size: 142,848 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 08 May 2013
Payload: Compromises system security, Displays image

Arrival Details

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This backdoor drops the following copies of itself into the affected system and executes them:

  • %User Temp%\{random file name 2}.pre - deleted afterwards
  • %User Temp%\{random folder name}\{random 1}tvyz.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.)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • LDRBCCE01

It injects codes into the following process(es):

  • svchost.exe
  • ctfmon.exe
  • explorer.exe

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random 2}tvyz.exe = "%User Temp%\{random folder name}\{random 1}tvyz.exe"

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Download and execute/load arbitrary .exe and .dll files
  • Update itself
  • Update C&C servers
  • Delete ntldr and ntdetect.com, then wipe MBR
  • Lock/unlock computer

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • http://{BLOCKED}xrz.com/typo3.php
  • http://{BLOCKED}ect-proxy.com/typo3.php
  • http://{BLOCKED}nes.com/t.php
  • http://{BLOCKED}line.com/t.php
  • http://{BLOCKED}olderxx.com/forums.php
  • http://{BLOCKED}bspace-apo.com/forums.php
  • http://{BLOCKED}eg.com/forums.php
  • http://{BLOCKED}k-gt.com/t po3.php
  • http://{BLOCKED}xrz.com/typo3.php
  • http://{BLOCKED}ect-proxy.com/typo3.php
  • http://{BLOCKED}nes.com/t.php
  • http://{BLOCKED}line.com/t.php
  • http://{BLOCKED}olderxx.com/forums.php
  • http://{BLOCKED}bspace-apo.com/forums.php

It posts the following information to its command and control (C&C) server:

  • Disk serial number
  • Attack status
  • Location
  • OS version

Other Details

This backdoor displays the following message boxes:


NOTES:
It terminates itself if the following string is found in its file path:

  • sand-box

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 9.920.04
FIRST VSAPI PATTERN DATE: 15 May 2013
VSAPI OPR PATTERN File: 9.921.00
VSAPI OPR PATTERN Date: 15 May 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

Restart in Safe Mode

[ Learn More ]

Step 3

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
    • {random 2}tvyz.exe = "%User Temp%\{random folder name}\{random 1}tvyz.exe"

Step 4

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