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Ransom.Win32.CRYTEM.A

September 07, 2019
 Analysis by: Henry Alarcon Jr.
 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

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.

  TECHNICAL DETAILS

File Size:

326,656 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

05 Sep 2019

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.

This malware arrives via the following means:

  • Saved inside the following registry key:
    • HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\SharedScripts\BIN_01

Other System Modifications

This Ransomware adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
.NETFramework\SecurityFolders
UserAgent = {data}

  • After encryption routine

Other Details

This Ransomware requires the existence of the following files to properly run:

  • MyPubKeyPwd@123
  • CNBPW42.DAT
  • Encryption Routine: CNBPW41.DAT
  • Decryption Routine: CNBPW40.DAT

It does the following:

  • Creates and deletes "__DirTest" file on all available drives and folders to test accessibility while listing files to encrypt
  • Encrypts files in all available drives, when the following conditions are met:
    • The environment variable "VS100WOW64MODE" is set to "True"
    • Required components exists
  • Decrypts files in all available drives, when the following conditions are met:
    • The following registry entry exists:
      • Key: oftware\Microsoft\.NETFramework\SecurityFolders
        Value: UserPassword
    • The environment variable "VS100WOW64MODE" is set to "True"
    • Successful connection to a named pipe "\.\pipe\UxdEvent_API_Service" and receive a command
    • Required components exists
  • It adds the following process:
    • C:\Windows\system32\cmd.exe /c powershell Start-Process -FilePath iexplore -ArgumentList "http://10.{BLOCKED}.{BLOCKED}.247/count02"

Ransomware Routine

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

  • %SystemRoot%
  • %ProgramFiles%
  • %ProgramFiles(x86)%
  • %ProgramW6432%
  • %SystemDrive%\Boot
  • %SystemDrive%\Config.Msi
  • %SystemDrive%\MSOCache
  • %SystemDrive%\PerfLogs
  • %SystemDrive%\ProgramData
  • %SystemDrive%\Recovery
  • %SystemDrive%\Users\*\AppData
  • %SystemDrive%\Users\*\Contacts
  • %SystemDrive%\Users\*\Favorites
  • %SystemDrive%\Users\*\Links
  • %SystemDrive%\Users\*\Searches
  • %SystemDrive%\Users\Default
  • %SystemDrive%\Users\Public
  • %SystemDrive%\DocumentsandSettings\*\ApplicationData
  • %SystemDrive%\DocumentsandSettings\*\Cookies
  • %SystemDrive%\DocumentsandSettings\*\Favorites
  • %SystemDrive%\DocumentsandSettings\*\LocalSettings
  • %SystemDrive%\DocumentsandSettings\*\NetHood
  • %SystemDrive%\DocumentsandSettings\*\PrintHood
  • %SystemDrive%\DocumentsandSettings\*\Recent
  • %SystemDrive%\DocumentsandSettings\*\SendTo
  • %SystemDrive%\DocumentsandSettings\*\StartMenu
  • %SystemDrive%\DocumentsandSettings\*\Templates
  • %SystemDrive%\DocumentsandSettings\AllUsers
  • %SystemDrive%\DocumentsandSettings\DefaultUser
  • %SystemDrive%\DocumentsandSettings\LocalService
  • %SystemDrive%\DocumentsandSettings\NetworkService
  • ?:\SystemVolumeInformation
  • *.dll
  • *.exe
  • *.sys
  • *.ini
  • *.mui
  • *.lnk
  • *NTUSER.DAT*
  • bootmgr
  • BOOTSECT.BAK
  • AUTOEXEC.BAT
  • NTDETECT.COM

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.346.05

FIRST VSAPI PATTERN DATE:

05 Sep 2019

VSAPI OPR PATTERN File:

15.347.00

VSAPI OPR PATTERN Date:

06 Sep 2019

Step 1

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 2

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 3

Identify and terminate files detected as Ransom.Win32.CRYTEM.A

[ 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 4

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.

 
  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFrework\SecurityFolders

Step 5

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

Step 6

Restore encrypted files from backup.


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