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Ransom.MSIL.AVEST.A

January 28, 2020
 ALIASES:

Ransom-Avest!54465F04A607 (NAI); W32/Ransom.A (exact) (FPROT)

 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, Dropped by other malware

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:

264,704 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

28 Aug 2019

Payload:

Displays graphics/image, 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:

  • {My Documents folder}\MyPictures\officeUpdate.exe
  • {First writable directory per drive}\googleupdate.exe (if file name contains DJVU, INSTALLER, AVEST, OFFICEUPDATE.EXE)
  • {Files targeted by %Desktop% shortcuts}

(Note: %Desktop% is the current user's desktop, which is usually C:\Documents and Settings\{User Name}\Desktop on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\Desktop on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It drops the following files:

  • {My Documents folder}\MyPictures\details.txt ⟵ contains random 8-character key

It adds the following processes:

  • "%System%\taskkill.exe" /F /IM WINWORD*
  • "%System%\taskkill.exe" /F /IM EXCEL*
  • "%System%\taskkill.exe" /F /IM 1c*
  • "%System%\taskkill.exe" /F /IM notepad*

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

Autostart Technique

This Ransomware drops the following file(s) in the Windows Common Startup folder to enable its automatic execution at every system startup:

  • %Common Startup%\officeupdate.lnk ⟵ points to {My Documents folder}\MyPictures\officeUpdate.exe (if file name contains DJVU, INSTALLER, AVEST, OFFICEUPDATE.EXE)

(Note: %Common Startup% is the startup folder for all users, which is usually C:\Documents and Settings\All Users\Start Menu\Programs\Startup on Windows 2000, XP, and Server 2003, or C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

Other System Modifications

This Ransomware deletes the following files:

  • Shortcut files in %Desktop%

(Note: %Desktop% is the current user's desktop, which is usually C:\Documents and Settings\{User Name}\Desktop on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\Desktop on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

Other Details

This Ransomware does the following:

  • Log off all Remote Desktop Services (RDS) sessions.
  • Rename all files targeted by %Desktop% shortcuts as {Original filename}64.{Original file extension}.
  • Propagate using Remote Desktop Protocol (RDP).

(Note: %Desktop% is the current user's desktop, which is usually C:\Documents and Settings\{User Name}\Desktop on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\Desktop on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It locks the screen and displays the following image:

Ransomware Routine

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

  • .ckey({Random 8-character key}).email data1992@{BLOCKED}mail.com).pack14

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

  • !!!Readme!!!Help!!!.txt

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

  • Problems with your data? Contact us: data1992@{BLOCKED}mail.com
    key: {Random 8-character key}

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.614.07

FIRST VSAPI PATTERN DATE:

11 Jan 2020

VSAPI OPR PATTERN File:

15.615.00

VSAPI OPR PATTERN Date:

12 Jan 2020

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.XXPE50FFF033

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.
  • {My Documents folder}\MyPictures\officeUpdate.exe
  • {First writable directory per drive}\googleupdate.exe
  • {Files targeted by %Desktop% shortcuts}
  • %Common Startup%\officeupdate.lnk

Step 6

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