Ransom.Win32.GANDCRAB.THOAAFAI

 Analysis by: Carl Maverick Pascual

 ALIASES:

Trojan-Ransom.Win32.GandCrypt.hdu (Kaspersky) ; Win32/Filecoder.GandCrab.D trojan (NOD32)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: Yes

  • 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:

304,128 bytes

File Type:

EXE

Initial Samples Received Date:

17 Jan 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 files:

  • {Encrypted Directory}\{random}.lock

Other System Modifications

This Ransomware adds the following registry entries as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\ex_data\
data
ext = {hex values}

HKEY_LOCAL_MACHINE\Software\KEYS_DATA\
data
private = {hex values}

HKEY_LOCAL_MACHINE\Software\KEYS_DATA\
data
public = {hex values}

Ransomware Routine

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

  • .{random}

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

  • {Encrypted Directory}\{random}-DECRYPT.txt

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.754.03

FIRST VSAPI PATTERN DATE:

16 Jan 2019

VSAPI OPR PATTERN File:

14.755.00

VSAPI OPR PATTERN Date:

17 Jan 2019

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.Win32.GANDCRAB.THOAAFAI

[ 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

Delete this registry key

[ 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\ex_data\data
    • ext = {hex values}
  • In HKEY_LOCAL_MACHINE\Software\kEYS_DATA\data
    • private = {hex values}
  • In HKEY_LOCAL_MACHINE\Software\KEYS_DATA\data
    • public = {hex values}

Step 5

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.
  • {Encrypted Directory}\{random}.lock

Step 6

Restore encrypted files from backup.

Step 7

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.GANDCRAB.THOAAFAI. 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:


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