Analysis by: Patrick Noel Collado
ALIASES:

W32/Kryptik.HKUF!tr (Fortinet), Win32/Kryptik.HKUG trojan (Nod32)

 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, Propagates via network shares

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 propagates via shared networks and drops copies of itself into available networks.

It drops files as ransom note.

  TECHNICAL DETAILS

File Size: 385,024 bytes
File Type: EXE
Memory Resident: Yes
Payload: Terminates processes, 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 copies of itself into the affected system:

  • {Malware Path}\{4 random digits}r.exe
  • {Malware Path}\{9 random characters}lan.exe

It adds the following processes:

  • "{Malware Path}\{4 random digits}r.exe" 9 REP
  • "{Malware Path}\{9 random characters}lan.exe" 8 LAN
  • cacls ""{Drive letter}:\*"" /grant Everyone:F /T /C /Q
  • net stop "{Service Name}"" /y
  • taskkill /IM /F {Process Name}
  • schtask /Create /S {remote machine} /TN {name of scheduled task} /TR "" /sc once /st 00:00 /RL HIGHEST

Propagation

This Ransomware propagates via shared networks and drops copies of itself into available networks.

Process Termination

This Ransomware terminates processes or services that contain any of the following strings if found running in the affected system's memory:

  • Processes:
    • 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
  • Services:
    • vmcomp
    • vmwp
    • veeam
    • back
    • xchange
    • ackup
    • acronis
    • sql
    • enterprise
    • sophos
    • acrsch
    • antivirus
    • bedbg
    • dcagent
    • epsecurity
    • epupdate
    • eraser
    • esgshkernel
    • fa_scheduler
    • iisadmin
    • imap4
    • mbam
    • endpoint
    • afee
    • mshield
    • 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

Ransomware Routine

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

  • ntldr
  • bootmgr
  • boot
  • NTDETECT

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

  • \Windows\
  • Windows
  • boot
  • WINDOWS
  • Chrome
  • Mozilla
  • SYSVOL
  • NTDS
  • netlogon
  • sysvol

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

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 16.710.03
FIRST VSAPI PATTERN DATE: 10 May 2021
VSAPI OPR PATTERN File: 16.711.00
VSAPI OPR PATTERN Date: 11 May 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.XXPE50FFF044

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

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

[ 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 5

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.
{Malware Path}\{4 random digits}r.exe
{Malware Path}\{9 random characters}lan.exe
{Encrypted Directory}\RyukReadMe.html

Step 6

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.RYUK.FAIMDER. 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:

Step 7

Restore encrypted files from backup.


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