Analysis by: John Anthony Banes
 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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.

It drops files as ransom note.

  TECHNICAL DETAILS

File Size: 753,704 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 18 Sep 2019

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 copies of itself into the affected system and executes them:

  • %Temp%\{malware name}_{random numbers}.exe

(Note: %Temp% is the Windows temporary folder, where it usually is C:\Windows\Temp on all Windows operating system versions.)

It drops the following files:

  • %Temp%\whytltozW8-0.cmd
  • %Temp%\whytltozW8-1.cmd
  • %Temp%\whytltozW8-2.cmd

(Note: %Temp% is the Windows temporary folder, where it usually is C:\Windows\Temp on all Windows operating system versions.)

It adds the following processes:

  • "%Temp%\whytltozW8-0.cmd" %System%\vssadmin.exe
  • {malware path and filename} +
  • {malware name}_{random numbers} 1
  • {malware name}_{random numbers} 2

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

Ransomware Routine

This Ransomware appends the following extension to the file name of the encrypted files:

  • .m3gac0rtx

It drops the following file(s) as ransom note:

  • {Drive Letter}:\!-!_README_!-!.rtf
  • %Desktop%\!-!_README_!-!.rtf

(Note: %Desktop% is the current user's desktop, which is usually C:\Documents and Settings\{User Name}\Desktop on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\Desktop on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 15.374.08
FIRST VSAPI PATTERN DATE: 18 Sep 2019
VSAPI OPR PATTERN File: 15.375.00
VSAPI OPR PATTERN Date: 19 Sep 2019

Step 1

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 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

Identify and terminate files detected as Ransom.Win32.MEGACORTEX.AC

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 4

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.
  • %Temp%\whytltozW8-0.cmd
  • %Temp%\whytltozW8-1.cmd
  • %Temp%\whytltozW8-2.cmd
  • {Drive Letter}:\!-!_README_!-!.rtf
  • %Desktop%\!-!_README_!-!.rtf

Step 5

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.MEGACORTEX.AC. 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 the following Trend Micro Support pages for more information:

Step 6

Restore encrypted files from backup.


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