Author: Carl Maverick Pascual   

 

Gen:Variant.Ransom.LockerGoga.4 (BitDefender) ; a variant of Win32/Filecoder.LockerGoga.D trojan (ESET-Nod32)

 PLATFORM:

Windows

 OVER ALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE
Low
Medium
High
Critical

  • Threat Type:
    Ransomware

  • Destructiveness:
    Yes

  • Encrypted:
    No

  • In the wild:
    Yes

  OVERVIEW

INFECTION CHANNEL: 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 encrypts files with specific file extensions. It encrypts files found in specific folders.

  TECHNICAL DETAILS

File size: 1,268,600 bytes
File type: EXE
Memory resident: No
INITIAL SAMPLES RECEIVED DATE: 19 March 2019
PAYLOAD: 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 copies of itself into the affected system:

  • %User Temp%\tgytutrc{4-Random Numbers}.exe

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, and 8.)

It adds the following processes:

  • %User Temp%\tgytutrc{4-Random Numbers}.exe -m
  • %User Temp%\tgytutrc{4-Random Numbers}.exe -i SM-tgytutrc -s

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, and 8.)

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

  • MX-tgytutrc

Other System Modifications

This Ransomware modifies the following registry entries:

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
RestartManager\Session00{01-20}
RegFiles00{00-20} = {Encrypted File}

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
RestartManager\Session00{01-20}
RegFilesHash = {Hex Values}

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
RestartManager\Session00{01-20}
Sequence = 0x00000001

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
RestartManager\Session00{01-20}
SessionHash = {Hex Values}

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
RestartManager\Session00{01-20}
Owner = {Hex Values}

Other Details

This Ransomware does the following:

  • Modifies the password of all installed user accounts to "HuHuHUHoHo283283@dJD"
  • It moves copies of itself to the %User Temp% directory before proceeding with its encryption routine
  • It attempts to log out local and remote sessions
  • It attempts to disable installed network adapters

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, and 8.)

Ransomware Routine

This Ransomware encrypts files with the following extensions:

  • all file types

It encrypts files found in the following folders:

  • Drives of the following type:
    • Fixed
    • Removable
    • Remote
    • Ramdisk

It avoids encrypting files found in the following folders:

  • %Windows%

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

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

  • .locked

It leaves text files that serve as ransom notes containing the following text:

  • %System Root%\Users\Public\Desktop\README_LOCKED.txt

  SOLUTION

Minimum scan engine: 9.850
First VSAPI Pattern File: 14.880.07
First VSAPI Pattern Release Date: 19 March 2019
VSAPI OPR PATTERN-VERSION: 14.881.00
VSAPI OPR PATTERN DATE: 20 March 2019

Step 1

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 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.LOCKERGOGA.AA

[ learnMore ]
  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

[ learnMore ]

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.

  • HKEY_CURRENT_USER\Software\Microsoft\RestartManager\Session00{00-20}

Step 5

Search and delete this file

[ learnMore ]
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.  
  • %System Root%\Users\Public\Desktop\README_LOCKED.txt

Step 6

Restore encrypted files from backup.

Step 7

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.LOCKERGOGA.AA. 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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