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Ransom.Win32.AKOLOCKER.A

January 23, 2020
 Analysis by: Earle Maui Earnshaw
 ALIASES:

Trojan.Win32.DelShad.cbx (Kaspersky); Ransom:Win32/MedusaLocker!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

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 drops files as ransom note. It avoids encrypting files with the following file extensions.

  TECHNICAL DETAILS

File Size:

605,696 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

10 Jan 2020

Payload:

Connects to URLs/IPs, 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 drops the following files:

  • {Encrypted Path}\id.key → encryption key
  • {Encrypted Directory}\ako-readme.txt → ransom note

It adds the following processes:

  • vssadmin.exe Delete Shadows /All /Quiet
  • bcdedit.exe /set {default} recoveryenabled No
  • bcdedit.exe /set {default} bootstatuspolicy ignoreallfailures
  • wbadmin DELETE SYSTEMSTATEBACKUP
  • wbadmin DELETE SYSTEMSTATEBACKUP -deleteOldest
  • wmic.exe SHADOWCOPY /nointeractive

Other System Modifications

This Ransomware modifies the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
System
EnableLinkedConnections = 1

Other Details

This Ransomware adds the following registry keys:

HKEY_CURRENT_USER\Software\akocfg
aid = .{Appended File Extension}

It does the following:

  • List all network adapters and it's associated IP addresses
  • Tor payment site for the ransomware:
    • http://{BLOCKED}hkidrby4mccwqpds5za6uo2thcw5gz75qncv7rbhyad.onion/{BLOCKED}U3PNABN

Ransomware Routine

This Ransomware avoids encrypting files with the following strings in their file path:

  • $
  • AppData
  • Program Files
  • Program Files (x86)
  • AppData
  • boot
  • PerfLogs
  • ProgramData
  • Google
  • Intel
  • Microsoft
  • Application Data
  • Tor Browser
  • Windows

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

  • .{6 random characters}

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

  • {Encrypted folder path}\ako-readme.txt

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

It avoids encrypting files with the following file extensions:

  • .exe
  • .dll
  • .sys
  • .ini
  • .lnk
  • .key
  • .rdp

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.618.02

FIRST VSAPI PATTERN DATE:

13 Jan 2020

VSAPI OPR PATTERN File:

15.619.00

VSAPI OPR PATTERN Date:

14 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

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_CURRENT_USER\Software\akocfg
    • aid = ".{Appended Extension}"

Step 6

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
    • EnableLinkedConnections = From: "1" To: "{Default}"

Step 7

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 Path}\id.key
  • {Encrypted Directory}\ako-readme.txt

Step 8

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 9

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 10

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win32.AKOLOCKER.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 11

Restore encrypted files from backup.

Step 12

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.AKOLOCKER.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 the following Trend Micro Support pages for more information:


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