arrow_back
search
close

Ransom.Win32.AVOSLOCKER.YPBLU

December 27, 2021
 Analysis by: Warren Adam Sto. Tomas
 ALIASES:

Ransom:Win32/AvosLocker.MBK!MTB (Microsoft)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • 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 is capable of encrypting files in the affected system.

It drops files as ransom note.

  TECHNICAL DETAILS

File Size:

826,880 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

21 Dec 2021

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 adds the following processes:

  • cmd /c wmic shadowcopy delete /nointeractive
  • cmd /c vssadmin.exe Delete Shadows /All Quiet
  • cmd /c bcdedit /set {default} recoveryenabled No
  • cmd /c bcdedit /set {default} bootstatuspolicy ignoreallfailures
  • cmd /c powershell -command "Get-EventLog -LogName * | ForEach { Clear-EventLog $_.Log }"

Other Details

This Ransomware is capable of encrypting files in the affected system.

Ransomware Routine

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

  • .avos2

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

  • {Encrypted directory}\GET_YOUR_FILES_BACK.txt

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

17.266.04

FIRST VSAPI PATTERN DATE:

21 Dec 2021

VSAPI OPR PATTERN File:

17.267.00

VSAPI OPR PATTERN Date:

22 Dec 2021

Step 1

Trend Micro Predictive Machine Learning detects and blocks malware at the first sign of its existence, before it executes on your system. When enabled, your Trend Micro product detects this malware under the following machine learning name:

     
    • Ransom.Win32.TRX.XXPE50FFF051

Step 2

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 3

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 4

Identify and terminate files detected as Ransom.Win32.AVOSLOCKER.YPBLU

[ 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 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}\GET_YOUR_FILES_BACK.txt

Step 6

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.AVOSLOCKER.YPBLU. 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 7

Enabling Volume Shadow Service

  1. Run the command prompt (cmd.exe) as administrator.
  2. Enable Volume Shadow Service by typing the following command:
    net start vss

Step 8

Enabling Windows Error Recovery

  1. Run the command prompt (cmd.exe) as administrator.
  2. Enable Windows Error Recovery Screen on Startup by typing the following command:
    bcdedit /set {default} bootstatuspolicy displayallfailures

Step 9

Enabling Startup Repair

  1. Run the command prompt (cmd.exe) as administrator.
  2. Enable Startup Repair by typing the following command:
    /bcedit /set {default} recoveryenabled Yes

Step 10

Restore encrypted files from backup.


Did this description help? Tell us how we did.