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Ransom.Win32.DEARCRY.THCABBA

March 15, 2021
 Analysis by: Thea Patrice Tajonera
 ALIASES:

Ransom:Win32/DoejoCrypt.A (MICROSOFT)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: No

  • 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.

  TECHNICAL DETAILS

File Size:

1,322,496 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

12 Mar 2021

Payload:

Drops files, 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.

Other Details

This Ransomware encrypts files with the following extensions:

  • .TIF
  • .TIFF
  • .PDF
  • .XLS
  • .XLSX
  • .XLTM
  • .PS
  • .PPS
  • .PPT
  • .PPTX
  • .DOC
  • .DOCX
  • .LOG
  • .MSG
  • .RTF
  • .TEX
  • .TXT
  • .CAD
  • .WPS
  • .EML
  • .INI
  • .CSS
  • .HTM
  • .HTML
  • .XHTML
  • .JS
  • .JSP
  • .PHP
  • .KEYCHAIN
  • .PEM
  • .SQL
  • .APK
  • .APP
  • .BAT
  • .CGI
  • .ASPX
  • .CER
  • .CFM
  • .C
  • .CPP
  • .GO
  • .CONFIG
  • .PL
  • .PY
  • .DWG
  • .XML
  • .JPG
  • .BMP
  • .PNG
  • .EXE
  • .DLL
  • .CAD
  • .AVI
  • .H
  • .CSV
  • .DAT
  • .ISO
  • .PST
  • .PGD
  • .7Z
  • .RAR
  • .ZIP
  • .ZIPX
  • .TAR
  • .PDB
  • .BIN
  • .DB
  • .MDB
  • .MDF
  • .BAK
  • .LOG
  • .EDB
  • .STM
  • .DBF
  • .ORA
  • .GPG
  • .EDB
  • .MFS

It does the following:

  • It encrypts files on all drives except for the following:
    • CD-ROM drive
  • It will proceed to its encryption routine when ran as a service named "msupdate"
  • The service is stopped and deleted when the encryption routine is finished
  • The ransomware prepends the string, "DEARCRY!", at the beginning of each encrypted file

Ransomware Routine

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

  • readme.txt

It avoids encrypting files found in the following folders:

  • %Windows%
  • %User Temp%
  • %Application Data%

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.. %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).. %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 appends the following extension to the file name of the encrypted files:

  • {Original Filename}\{Original File Extension}.CRYPT

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

  • {Encrypted Directory}\readme.txt
  • %Desktop%\readme.txt

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

16.590.01

FIRST VSAPI PATTERN DATE:

12 Mar 2021

VSAPI OPR PATTERN File:

16.591.00

VSAPI OPR PATTERN Date:

13 Mar 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:

    • Ransom.Win32.TRX.XXPE50FFF042E0002

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

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 Directory}\readme.txt
  • %Desktop%\readme.txt

Step 5

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.DEARCRY.THCABBA. 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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