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Ransom.Win32.MCRYPT.A

September 11, 2019
 Analysis by: Jay Garcia
 ALIASES:

Trojan-Ransom.Win32.Dcryptor.g (Kaspersky); Trojan-Spy.Win32.Gaxfid (Ikarus)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet


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

  TECHNICAL DETAILS

File Size:

1,450,496 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

23 Aug 2019

Payload:

Displays message/message boxes, Drops files, Encrypts files

Arrival Details

This Ransomware 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 Ransomware drops the following files:

  • %System%\drivers\dcrypt.sys
  • {malware path}\dcapi.dll
  • {malware path}\dccrypt.sys
  • {malware path}\igfxen.exe - detected as PUA.Win32.DiskCrypt.A

It drops and executes the following files:

  • {malware path}\inst32.exe - if machine is 32bit
    {malware path}\inst64.exe - if machine is 64bit

Autostart Technique

This Ransomware registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\dcrypt\Instances
DefaultInstance = dcrypt

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\dcrypt\Instances\
dcrypt
Altitude = 87150

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\dcrypt\Instances\
dcrypt
Flags = 0

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\dcrypt\config
Flags = 0

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\dcrypt\config
Hotkeys = 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\dcrypt\config
sysbuild = 846

It adds and runs the following services:

  • dcrypt

Other System Modifications

This Ransomware adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\dcrypt\Instances

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\dcrypt\Instances\
dcrypt

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\dcrypt\config

Other Details

This Ransomware does the following:

  • After booting up your system, it will display the following ransom note:
  • It modifies the Master Boot Record to display the ransom note
  • The dropped file {malware path}\igfxen.exe requires specific arguments to perform it's malicious routine

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.334.05

FIRST VSAPI PATTERN DATE:

30 Aug 2019

VSAPI OPR PATTERN File:

15.335.00

VSAPI OPR PATTERN Date:

31 Aug 2019

Step 1

Trend Micro Predictive Machine Learning detects and blocks malware at the first sign of its existence, before it executes on your system. When enabled, your Trend Micro product detects this malware under the following machine learning name:

     
    • Troj.Win32.TRX.XXPE50FFF031

Step 2

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 users must disable System Restore to allow full scanning of their computers.

Step 3

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 4

Restore your system's Master Boot Record (MBR)

To restore your system's Master Boot Record (MBR):

• On Windows 7 and Server 2008 (R2):

  1. Insert your Windows Installation DVD into the DVD drive, then press the restart button on your computer.
  2. When prompted, press any key to boot from the DVD.
  3. Depending on your Windows Installation DVD, you might be required to choose the installation language. On the Install Windows window, choose your language, locale, and keyboard layout or input method. Click Repair your computer.
  4. Select Use recovery tools that can help fix problems starting Windows. Select your installation of Windows. Click Next.
  5. If the Startup Repair window appears, click Cancel, Yes, then Finish.
  6. In the System Recovery Options menu, click Command Prompt.
  7. In the Command Prompt window, type the following then press Enter:
    BootRec.exe /fixmbr
  8. Type exit and press Enter to close the Command Prompt window.
  9. Click Restart to restart your computer normally.

• On Windows 8, 8.1, 10, and Server 2012:

  1. Insert your Windows Installation DVD in the DVD drive, then restart your computer.
  2. When prompted, press any key to boot from the DVD.
  3. Depending on your Windows Installation DVD, you might be required to select the keyboard layout. Then on the Windows Setup window, choose your language, locale, and input method. Click Next, then click Repair your computer.
  4. Click Troubleshoot>Advanced Options>Command Prompt.
  5. In the Command Prompt window, type the following then press Enter:
    BootRec.exe /fixmbr
  6. Type exit and press Enter to close the Command Prompt window.
  7. Click Continue to restart the system normally.

Step 5

Restart in Safe Mode

[ Learn More ]

Step 6

Delete this registry key

[ 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_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\dcrypt
    • Instances
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\dcrypt
    • config

Step 7

Search and delete this file

[ 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.
  • %System%\drivers\dcrypt.sys
  • {malware path}\dcapi.dll
  • {malware path}\dccrypt.sys
  • {malware path}\igfxen.exe
  • {malware path}\inst32.exe - if machine is 32bit
  • {malware path}\inst64.exe - if machine is 64bit

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win32.MCRYPT.A. 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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