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RANSOM_MADLOCKER.BYX

June 02, 2016
 Analysis by: Michael Jay Villanueva
 ALIASES:

Trojan:Win32/Dynamer!ac (Microsoft); Trojan.Win32.Deshacop.coj (Kaspersky); TR/Deshacop.dfgh (Avira)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet


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

It connects to certain websites to send and receive information. However, as of this writing, the said sites are inaccessible. It deletes itself after execution. It is capable of encrypting files in the affected system.

  TECHNICAL DETAILS

File Size:

314,880 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

23 May 2016

Payload:

Connects to URLs/IPs, Encrypts files

Arrival Details

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

  • %All Users Profile%\svchosd.exe

(Note: %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It drops the following files:

  • %All Users Profile%\decrypting.txt
  • %All Users Profile%\start.txt
  • %All Users Profile%\cryptinfo.txt -> Ransom Note
  • %All Users Profile%\date_1.txt
  • %All Users Profile%\select.bat

(Note: %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

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
Windows Firewall = %All Users Profile%\svchosd.exe

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Windows Update = %All Users Profile%\select.bat

Other Details

This Trojan connects to the following website to send and receive information:

  • http://{BLOCKED}.{BLOCKED}.192.88

However, as of this writing, the said sites are inaccessible.

It deletes itself after execution.

It is capable of encrypting files in the affected system.

NOTES:

This ransomware avoids encrypting files in the following file paths:

  • \Windows\
  • \WINDOWS\
  • \Program Files\
  • \Program Files (x86)\
  • Games
  • \Temp
  • \Sample Pictures
  • \Sample Music
  • \cache
  • \Cache

It executes the following command to delete shadow copies:

vssadmin.exe delete shadows /for=%c: /All /Quiet

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

12.544.07

FIRST VSAPI PATTERN DATE:

23 May 2016

VSAPI OPR PATTERN File:

12.545.00

VSAPI OPR PATTERN Date:

24 May 2016

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

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

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\CurrentVersion\Run
    • Windows Firewall = %All Users Profile%\svchosd.exe
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Windows Update = %All Users Profile%\select.bat

Step 5

Remove the malware/grayware file that dropped/downloaded RANSOM_MADLOCKER.BYX. (Note: Please skip this step if the threat(s) listed below have already been removed.)

Step 6

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.
  • %All Users Profile%\svchosd.exe
  • %All Users Profile%\decrypting.txt
  • %All Users Profile%\start.txt
  • %All Users Profile%\cryptinfo.txt
  • %All Users Profile%\date_1.txt
  • %All Users Profile%\select.bat

Step 7

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