Analysis by: Maria Emreen Viray
ALIASES:

Ransom:Win32/MedusaLocker.A!MTB (MICROSOFT); Trojan-Ransom.Win32.Medusa.aj (KASPERSKY)

 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, 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 encrypts files found in specific folders. It drops files as ransom note. It avoids encrypting files with the following file extensions.

  TECHNICAL DETAILS

File Size: 694,784 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 17 Jun 2021
Payload: Drops files, Terminates processes

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:

  • %Application Data%\svhost.exe

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

It adds the following processes:

  • to delete backup files:
    • 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

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

  • {8761ABBD-7F85-42EE-B272-A76179687C63}

Other System Modifications

This Ransomware modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
System
EnableLUA = 0

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
System
ConsentPromptBehaviorAdmin = 0

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

Process Termination

This Ransomware terminates the following services if found on the affected system:

  • ccEvtMgr
  • ccSetMgr
  • Culserv
  • dbeng8
  • dbsrv12
  • DefWatch
  • Intuit.QuickBooks.FCS
  • msmdsrv
  • QBCFMonitorService
  • QBIDPSerivce
  • RTVscan
  • SavRoam
  • sqladhlp
  • SQLADHLP
  • sqlagent
  • sqlbrowser
  • sqlservr
  • sqlwriter
  • tomcat6
  • vmware-converter
  • vmware-usbarbitator64
  • wrapper
  • zhudongfangyu

It terminates the following processes if found running in the affected system's memory:

  • 360doctor.exe
  • 360se.exe
  • axlbridge.exe
  • Culture.exe
  • Defwatch.exe
  • fdhost.exe
  • fdlauncher.exe
  • GDscan.exe
  • httpd.exe
  • java.exe
  • MsDtSrvr.exe
  • QBCFMonitorService.exe
  • QBDBMgr.exe
  • QBIDPService.exe
  • qbupdate.exe
  • QBW32.exe
  • RAgui.exe
  • RTVscan.exe
  • sqlbrowser.exe
  • sqlmangr.exe
  • sqlservr.exe
  • supervise.exe
  • tomcat6.exe
  • wdswfsafe.exe
  • winword.exe
  • wxServer.exe
  • ZhuDongFangYu.exe

Other Details

This Ransomware adds the following registry keys:

HKEY_CURRENT_USER\Software\MDSLK

It does the following:

  • checks privileges and can perform privilege escalation
  • encrypts all existing drives in the system and network shares
  • empties Recycle Bin
  • modifies registry entries to:
    • disables User Account Control (UAC)
    • perform operations that require elevation without consent
  • uses Restart Manager to unlock files before encryption

It adds the following scheduled tasks:

  • Name: svhost
    Trigger: Daily; At time of installation, repeat every 15 mins indefinitely
    Action: %Application Data%\svhost.exe

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

Ransomware Routine

This Ransomware encrypts files found in the following folders:

  • %Program Files%\Microsoft\Exchange Server
  • %Program Files% (x86)\Microsoft\Exchange Server
  • %Program Files%\Microsoft SQL Server
  • %Program Files% (x86)\Microsoft SQL Server

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000(32-bit), Server 2003(32-bit), XP, Vista(64-bit), 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit) , or C:\Program Files (x86) in Windows XP(64-bit), Vista(64-bit), 7(64-bit), 8(64-bit), 8.1(64-bit), 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It avoids encrypting files found in the following folders:

  • %All Users Profile%
  • %Program Files%
  • %Public%
  • %System Root%\AppData
  • %System Root%\Application Data
  • %System Root%\intel
  • %System Root%\nvidia
  • %Sytem Root%\Users\All Users
  • %User Profile%\AppData
  • %User Temp%
  • %Windows%

(Note: %All Users Profile% is the common user's profile folder, which is usually C:\Documents and Settings\All Users on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit). . %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000(32-bit), Server 2003(32-bit), XP, Vista(64-bit), 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit) , or C:\Program Files (x86) in Windows XP(64-bit), Vista(64-bit), 7(64-bit), 8(64-bit), 8.1(64-bit), 2008(64-bit), 2012(64-bit) and 10(64-bit).. %Public% is the folder that serves as a repository of files or folders common to all users, which is usually C:\Users\Public in Windows Vista, 7, and 8.. %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name} on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %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:

  • .ReadInstruction

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

It avoids encrypting files with the following file extensions:

  • file extensions:
    • .386
    • .adv
    • .ani
    • .bat
    • .bin
    • .cab
    • .cmd
    • .com
    • .cpl
    • .cur
    • .dll
    • .drv
    • .enc
    • .exe
    • .hiv
    • .hlp
    • .hta
    • .icl
    • .icns
    • .ico
    • .ics
    • .idx
    • .ini
    • .key
    • .ldf
    • .lnk
    • .lock
    • .log
    • .mod
    • .mpa
    • .msc
    • .msi
    • .msp
    • .msu
    • .nls
    • .ocx
    • .prf
    • .ps1
    • .rdp
    • .rom
    • .rtp
    • .scr
    • .shs
    • .spl
    • .sys
    • .theme
    • .wpx
  • ransomware extensions:
    • .AULOCK
    • .DEDE
    • .DELOCK
    • .DELOCKII
    • .DogUlitos
    • .FRFR
    • .GBLOCK
    • .HKLOCK
    • .HKLOCKII
    • .ILLOCK
    • .ITLOCK
    • .KRLOCK
    • .KRLOCK2
    • .KRLOCK3
    • .KRLOCK4
    • .LOCK
    • .NETFULL
    • .PedroChicken
    • .READINSTRUCTIONS
    • .ReadInsturction
    • .Readinstructions
    • .SQLITEDB
    • .cnlock
    • .cryptocrypto
    • .czlock
    • .datalock
    • .deadfiles
    • .delocks
    • .deskthemepack
    • .diagcab
    • .diagcfg
    • .diagpkg
    • .dodik
    • .eslock
    • .frlock
    • .grgr
    • .grlock
    • .hivteam
    • .hklockII
    • .hklockfiles
    • .hknet
    • .ielock
    • .itlock
    • .ittlock
    • .krnet
    • .local
    • .lockernetwork
    • .lockers
    • .lockes
    • .lockeu
    • .lockhk
    • .locklock
    • .lokes
    • .lvlock
    • .mdlock
    • .monster
    • .msstyles
    • .netATlock
    • .netAUlock
    • .netCAlock
    • .netCAlockII
    • .netFRlock
    • .netHKlock
    • .netIDlock
    • .netLAlock
    • .netMXlock
    • .netUSlock
    • .netca
    • .netlock
    • .netlockau
    • .netlockcn
    • .netlockcn2
    • .netlockcncn
    • .netlockkiosktw
    • .netlocklk
    • .netlockthth
    • .netlockuss
    • .networkmaze
    • .nomedia
    • .recoverme
    • .sglock
    • .shan
    • .shanghai
    • .shanghai2
    • .shanghai3
    • .shanghai4
    • .shanghai5
    • .shanghai6
    • .shanghai7
    • .shanghai8
    • .shanghai9
    • .stopfiles
    • .support
    • .themepack
    • .titan
    • .uslock
    • .uslockII
    • .uslockIII
    • .uslockIV
    • .uslockh
    • .uslockhh
    • .viets
    • .vnlock
    • .zalock

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 16.870.08
FIRST VSAPI PATTERN DATE: 28 Jul 2021
VSAPI OPR PATTERN File: 16.871.00
VSAPI OPR PATTERN Date: 29 Jul 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.XXPE50FLM011

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

Deleting Scheduled Tasks

The following {Task Name} - {Task to be run} listed should be used in the steps identified below:

  • Task Name: svhost
  • Task to be run: %Application Data%\svhost.exe

    • For Windows 2000, Windows XP, and Windows Server 2003:

    1. Open the Windows Scheduled Tasks. Click Start>Programs>Accessories>
      System Tools>Scheduled Tasks.
    2. Locate each {Task Name} values listed above in the Name column.
    3. Right-click on the said file(s) with the aforementioned value.
    4. Click on Properties. In the Run field, check for the listed {Task to be run}.
    5. If the strings match the list above, delete the task.

    For Windows Vista, Windows 7, Windows Server 2008, Windows 8, Windows 8.1, and Windows Server 2012:

    1. Open the Windows Task Scheduler. To do this:
      • On Windows Vista, Windows 7, and Windows Server 2008, click Start, type taskschd.msc in the Search input field, then press Enter.
      • On Windows 8, Windows 8.1, and Windows Server 2012, right-click on the lower left corner of the screen, click Run, type taskschd.msc, then press Enter.
    2. In the left panel, click Task Scheduler Library.
    3. In the upper-middle panel, locate each {Task Name} values listed above in the Name column.
    4. In the lower-middle panel, click the Actions tab. In the Details column, check for the {Task to be run} string.
    5. If the said string is found, delete the task.

    Step 6

    Delete this registry value

    [ 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\MDSLK
      • Self = {Malware Name}

    Step 7

    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\MDSLK

    Step 8

    Restore this modified registry value

    [ 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.

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
    • From EnableLUA = 0
    • To EnableLUA = {Default Value}
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
    • From ConsentPromptBehaviorAdmin = 0
    • To ConsentPromptBehaviorAdmin = {Default Value}
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
    • From EnableLinkedConnections = 1
    • To EnableLinkedConnections = {Default Value}

    Step 9

    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.
    • %Application Data%\svhost.exe
    • {Encrypted Directory}\Recovery_Instructions.html

    Step 10

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


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