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RANSOM_REBOLOCK.A

February 01, 2017
 Analysis by: Julie Anne Cabuhat
 ALIASES:

Ransom.Rebatsa (Malwarebytes), Trojan/Win32.Diztakun (Antiy-AVL)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware


This Trojan 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:

329,728 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

26 Jan 2017

Payload:

Encrypts files, Disables services

Arrival Details

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
LataReboLocker = "{malware path}\LataReboLocker.exe"

Other System Modifications

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

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

Other Details

This Trojan does the following:

  • It terminates explorer.exe using the following command:
    • "C:\WINDOWS\system32\taskkill.exe" /F /IM explorer.exe

NOTES:

The ransomware locks the screen with the following image:

If the "Insert Key" button is clicked without the correct key, the following message box is displayed:

;

The correct key is "Rebatsa". Entering the key will restart explorer.exe and enable the Task Manager and delete the auto-start registry. It will not terminate the program.

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

13.184.00

FIRST VSAPI PATTERN DATE:

26 Jan 2017

VSAPI OPR PATTERN File:

13.185.00

VSAPI OPR PATTERN Date:

27 Jan 2017

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • LataReboLocker = {malware path}\LataReboLocker.exe

Step 5

Enable Registry Editor, Task Manager, and Folder options

[ Learn More ]
By doing this step, you also enable other applications/programs disabled by this malware/grayware/spyware.

Step 6

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