Analysis by: Marcus Ma. Antonio Capistrano
ALIASES:

Ransomware-GJS!201C3E2C96C7 (NAI), a variant of MSIL/LockScreen.XP trojan (NOD32),MSIL/LockScreen.XP!tr (FORTINET)

 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

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 adds certain registry entries to disable the Task Manager. This action prevents users from terminating the malware process, which can usually be done via the Task Manager.

  TECHNICAL DETAILS

File Size: 29,696 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 18 Feb 2018
Payload: Disables services, Terminates processes

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.

Autostart Technique

This Ransomware adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
ByteLocker = {malware file path}\{malware file name}

Other System Modifications

This Ransomware adds the following registry entries to disable the Task Manager:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableTaskMgr = 1

Process Termination

This Ransomware terminates processes or services that contain any of the following strings if found running in the affected system's memory:

  • taskmgr
  • explorer
  • iexplore
  • firefox
  • winrar
  • WDExpress
  • chrome
  • SystemSettings

Other Details

This Ransomware does the following:

  • "Buy BitCoins" button will open a browser window which opens the site "https://buy.bitcoin.com/"
  • Entering "Key" on the Enter Decryption Key field and pressing "Unlock My Windows" re-enables task manager,starts windows explorer, and shows the following window:

  • Upon execution of the ransomware, it shows the following window in full screen, effectively locking the desktop:

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 13.976.04
FIRST VSAPI PATTERN DATE: 19 Feb 2018
VSAPI OPR PATTERN File: 13.977.00
VSAPI OPR PATTERN Date: 20 Feb 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

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
    • ByteLocker = {malware file path}\{malware file name}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System
    • DisableTaskMgr = 1

Step 5

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