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Ransom_MEDUZA.THHOBAH

August 14, 2018
 Analysis by: Noel Anthony Llimos
 ALIASES:

Gen:Heur.Ransom.Imps.1 (Bitdefender), Trojan:Win32/Occamy.B (Microsoft)

 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:

Downloaded from the Internet, Dropped by other malware

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:

17,920 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

02 Aug 2018

Payload:

Drops files, Terminates processes, Displays message/message boxes, 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:

  • %User Startup%\ITunes.hta ← It drops the following file to enable the ransom note to pop up at every system startup
  • %User Profile%\aesKey.bin

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows XP, or C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup on Windows Vista, 7, and 8.. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista, 7, and 8.)

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

  • NET CLR Google

Process Termination

This Ransomware terminates the following processes if found running in the affected system's memory:

  • notepad.exe
  • excel.exe
  • mysql.exe

Other Details

This Ransomware does the following:

  • It avoids encrypting files with the following extensions:
    • .exe
    • .dll
    • .ink
    • .meduza
    • .bin
  • It encrypts files found in all fixed, removable and network drives.
  • It displays the following upon successful encryption and at every system startup

Ransomware Routine

This Ransomware avoids encrypting files with the following strings in their file path:

  • $Recycle.Bin
  • Boost
  • ProgramData
  • Windows
  • ProgramFiles

It appends the following extension to the file name of the encrypted files:

  • .[cryhelp@tutanota.com].meduza

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

  • {Encrypted Directory}\!How_to_decrypt.txt

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.418.04

FIRST VSAPI PATTERN DATE:

02 Aug 2018

VSAPI OPR PATTERN File:

14.419.00

VSAPI OPR PATTERN Date:

03 Aug 2018

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

Identify and terminate files detected as Ransom_MEDUZA.THHOBAH

[ 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 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.  
  • %User Startup%\ITunes.hta
  • {Encrypted Directory}\!How_to_decrypt.txt
  • %User Profile%\aesKey.bin

Step 5

Scan your computer with your Trend Micro product to delete files detected as Ransom_MEDUZA.THHOBAH. 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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