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Ransom.Win32.AVOSLOCKER.A

August 31, 2021
 Analysis by: Thea Patrice Tajonera
 ALIASES:

Trojan-Ransom.Avaddon (IKARUS)

 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:

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 drops files as ransom note.

  TECHNICAL DETAILS

File Size:

412,160 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

27 Jul 2021

Payload:

Encrypts files, Displays message/message boxes

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 mutexes to ensure that only one of its copies runs at any one time:

  • ievah8eVki3Ho4oo

Other Details

This Ransomware does the following:

  • This Ransomware displays its encryption progress in console
  • It encrypts files found in the following drives:
    • Fixed Drives
    • Removable Drives
    • Network Share Drives
  • It checks if the file it tries to encrypt is being ran by another process
    • If the file is currently being used by another process, the ransomware kills the process and proceeds with encryption

It accepts the following parameters:

  • h -> hide the console
  • n -> skip encryption of network share drives

Ransomware Routine

This Ransomware encrypts files with the following extensions:

  • doc
  • docx
  • xls
  • xlsx
  • ppt
  • pptx
  • pst
  • ost
  • msg
  • eml
  • vsd
  • vsdx
  • txt
  • csv
  • rtf
  • wks
  • wk1
  • pdf
  • dwg
  • onetoc2
  • snt
  • jpeg
  • jpg
  • docb
  • docm
  • dot
  • dotm
  • dotx
  • xlsm
  • xlsb
  • xlw
  • xlt
  • xlm
  • xlc
  • xltx
  • xltm
  • pptm
  • pot
  • pps
  • ppsm
  • ppsx
  • ppam
  • potx
  • potm
  • edb
  • hwp
  • 602
  • sxi
  • sti
  • sldx
  • sldm
  • sldm
  • vdi
  • vmdk
  • vmx
  • gpg
  • aes
  • ARC
  • PAQ
  • bz2
  • tbk
  • bak
  • tar
  • tgz
  • gz
  • 7z
  • rar
  • zip
  • backup
  • iso
  • vcd
  • bmp
  • png
  • gif
  • raw
  • cgm
  • tif
  • tiff
  • nef
  • psd
  • ai
  • svg
  • djvu
  • m4u
  • m3u
  • mid
  • wma
  • flv
  • 3g2
  • mkv
  • 3gp
  • mp4
  • mov
  • avi
  • asf
  • mpeg
  • vob
  • mpg
  • wmv
  • fla
  • swf
  • wav
  • mp3
  • sh
  • class
  • jar
  • java
  • rb
  • asp
  • php
  • jsp
  • brd
  • sch
  • dch
  • dip
  • pl
  • vb
  • vbs
  • ps1
  • bat
  • cmd
  • js
  • asm
  • h
  • pas
  • cpp
  • c
  • cs
  • suo
  • sln
  • ldf
  • mdf
  • ibd
  • myi
  • myd
  • frm
  • odb
  • dbf
  • db
  • mdb
  • accdb
  • sql
  • sqlitedb
  • sqlite3
  • asc
  • lay6
  • lay
  • mml
  • sxm
  • otg
  • odg
  • uop
  • std
  • sxd
  • otp
  • odp
  • wb2
  • slk
  • dif
  • stc
  • sxc
  • ots
  • ods
  • 3dm
  • max
  • 3ds
  • uot
  • stw
  • sxw
  • ott
  • odt
  • pem
  • p12
  • csr
  • crt
  • key
  • pfx
  • der
  • dat

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

  • {Original Filename}\{Original Extension}.avos

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

  • %Desktop%\GET_YOUR_FILES_BACK.txt
  • {Encrypted Directory}\GET_YOUR_FILES_BACK.txt

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

16.898.03

FIRST VSAPI PATTERN DATE:

11 Aug 2021

VSAPI OPR PATTERN File:

16.899.00

VSAPI OPR PATTERN Date:

12 Aug 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:

     
    • Troj.Win32.TRX.XXPE50FFF046

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

Restart in Safe Mode

[ Learn More ]

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.
  • %Desktop%\GET_YOUR_FILES_BACK.txt
  • {Encrypted Directory}\GET_YOUR_FILES_BACK.txt

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win32.AVOSLOCKER.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.

Step 7

Restore encrypted files from backup.


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