Ransom.Win32.RYUK.HUD

December 30, 2019
 Analysis by: Patrick Angelo Roderno
 ALIASES:

a variant of Win32/Kryptik.GYIL trojan (ESET NOD32); W32/GenKryptik.DXQV!tr (FORTINET); Malware-Cryptor.Limpopo (VBA32)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: Yes

  • 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. It avoids encrypting files with the following file extensions.

  TECHNICAL DETAILS

File Size:

214,528 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

23 Nov 2019

Payload:

Collects system information, Drops files, Terminates processes, Displays message/message boxes, 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:

  • {malware path}\{random}.exe

It drops the following files:

  • %Public%\PUBLIC
  • %Public%\UNIQUE_ID_DO_NOT_REMOVE
  • %Public%\sys
  • %User Startup%\start.bat
  • %Common Startup%\start.bat
  • %System Root%\Document and Settings\Default User\window.bat
  • %Public%\finish

(Note: %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.. %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows 2003(32-bit), XP and 2000(32-bit), or C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit), 10(64-bit).. %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.. %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.)

Other Details

This Ransomware does the following:

  • It executes its copy having the following parameters:
    • {malware path}\{random}.exe 8 LAN
  • It searches for the following string in the machine's services. If the string is present in the service name, it will terminate the service by the following command "net stop "{service name}" /y":
    • vmcomp
    • vmwp
    • veeam
    • back
    • xchange
    • ackup
    • acronis
    • sql
    • enterprise
    • sophos
    • veeam
    • acrsch
    • antivirus
    • antivirus
    • bedbg
    • dcagent
    • epsecurity
    • epupdate
    • eraser
    • esgshkernel
    • fa_scheduler
    • iisadmin
    • imap4
    • mbam
    • endpoint
    • afee
    • mcshield
    • task
    • mfemms
    • mfevtp
    • mms
    • msdts
    • exchange
    • ntrt
    • pdvf
    • pop3
    • report
    • resvc
    • sacsvr
    • savadmin
    • sams
    • sdrsvc
    • sepmaster
    • monitor
    • smcinst
    • smcservice
    • smtp
    • snac
    • swi_
    • ccsf
    • truekey
    • tmlisten
    • ui0detect
    • w3s
    • wrsvc
    • netmsmq
    • ekrn
    • ehttpsrv
    • eshasrv
    • avp
    • klnagent
    • wbengine
    • kavf
    • mfefire
  • It terminates processes having the following strings, it uses "taskkill /IM /F {Process Name}" to terminate:
    • virtual
    • vmcomp
    • vmwp
    • veeam
    • backup
    • backup
    • xchange
    • sql
    • dbeng
    • sofos
    • calc
    • ekrn
    • zoolz
    • encsvc
    • excel
    • firefoxconfig
    • infopath
    • msaccess
    • mspub
    • mydesktop
    • ocautoupds
    • ocomm
    • ocssd
    • onenote
    • oracle
    • outlook
    • powerpnt
    • sqbcoreservice
    • steam
    • synctime
    • tbirdconfig
    • thebat
    • thunderbird
    • visio
    • word
    • xfssvccon
    • tmlisten
    • pccntmon
    • cntaosmgr
    • ntrtscan
    • mbamtray

Ransomware Routine

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

  • RyukReadMe.html
  • UNIQUE_ID_DO_NOT_REMOVE
  • PUBLIC
  • sysvol
  • netlogon
  • PRIVATE

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

  • \Windows\
  • AhnLab
  • Chrome
  • Mozilla
  • $Recycle.Bin
  • WINDOWS
  • bin
  • boot
  • dev
  • etc
  • lib
  • initrd
  • sbin
  • sys
  • vmlinuz
  • run
  • var

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

  • .RYK

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

  • {Encrypted directory}\RyukReadMe.html

It avoids encrypting files with the following file extensions:

  • dll
  • hrmlog
  • exe
  • .ini
  • .lnk

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.590.03

FIRST VSAPI PATTERN DATE:

30 Dec 2019

VSAPI OPR PATTERN File:

15.591.00

VSAPI OPR PATTERN Date:

31 Dec 2019

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.XXPE50FFF032

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

Identify and terminate files detected as Ransom.Win32.RYUK.HUD

[ 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 6

Search and delete this file

[ 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.
  • %Public%\PUBLIC
  • %Public%\UNIQUE_ID_DO_NOT_REMOVE
  • %Public%\sys
  • %Public%\finish
  • %User Startup%\start.bat
  • %Common Startup%\start.bat
  • %System Root%\Document and Settings\Default User\window.bat
  • {Encrypted directory}\RyukReadMe.html

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win32.RYUK.HUD. 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 8

Restore encrypted files from backup.


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