RANSOM_RANDOMLOCK.THDCOAH

May 11, 2018
 Analysis by: Michael Jhon Ofiaza
 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: Yes

  • 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.

It downloads a file from a certain URL then renames it before storing it in the affected system.

It connects to certain websites to send and receive information.

It encrypts files with specific file extensions. It encrypts files found in specific folders.

  TECHNICAL DETAILS

File Size:

37,376 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

20 Apr 2018

Payload:

Displays graphics/image, Displays windows, Terminates processes, Connects to URLs/IPs, Downloads 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:

  • {malware path}\wallpaper.png
  • %User Profile%\Pictures\wallpaper.png -> used as desktop wallpaper

(Note: %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 and 7.)

Other System Modifications

This Ransomware changes the desktop wallpaper by modifying the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = %User Profile%\Pictures\wallpaper.png

It sets the system's desktop wallpaper to the following image:

Process Termination

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

  • chrome
  • firefox
  • iexplore
  • taskmgr
  • cmd
  • Powershell

Download Routine

This Ransomware downloads files from the following URLs then renames them before storage in the affected system:

  • https://i.{BLOCKED}r.com/L2g45Xs.png

It saves the files it downloads using the following names:

  • {malware path}\wallpaper.png

Other Details

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

  • http://{BLOCKED}.{BLOCKED}.88.116/3DWYMbC9s3GMj7fj/adduser.php?id={username}{user domain name}&pass={key}

Ransomware Routine

This Ransomware encrypts files with the following extensions:

  • .bat
  • .hlp
  • .xml
  • .chm
  • .ini
  • .xls
  • .xlsx
  • .txt
  • .exe
  • .png
  • .jpg
  • .gif
  • .bmp
  • .pdf
  • .doc
  • .jpeg
  • .dll
  • .docx
  • .rar
  • .zip
  • .html
  • .php
  • .mp3
  • .mp4
  • .wav
  • .wmv

It encrypts files found in the following folders:

  • %Desktop%
  • %User Profile%\Documents
  • %User Profile%\Pictures
  • C:\Users\{Username}\Downloads
  • C:\Users\Public

(Note: %Desktop% is the desktop folder, where it usually is C:\Documents and Settings\{user name}\Desktop in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\Desktop in 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.. %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 and 7.)

It avoids encrypting files with the following strings in their file name:

  • {malware name}
  • wallpaper.png

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

  • .rand

NOTES:

This ransomware displays the following before encrypting files:

It also displays the following after encrypting files:

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.222.02

FIRST VSAPI PATTERN DATE:

30 Apr 2018

VSAPI OPR PATTERN File:

14.223.00

VSAPI OPR PATTERN Date:

01 May 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_RANDOMLOCK.THDCOAH

[ 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.
  • {malware path}\wallpaper.png
  • %User Profile%\Pictures\wallpaper.png

Step 5

Scan your computer with your Trend Micro product to delete files detected as RANSOM_RANDOMLOCK.THDCOAH. 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

Reset your Desktop properties

[ Learn More ]

Step 7

Restore encrypted files from backup.


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