Ransom.Win32.BACUCRYPT.A

September 21, 2023
 Analysis by: Raymart Christian Yambot
 ALIASES:

Generic.Ransom.Cuba.BBC6A0B5 (BITDEFENDER)

 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 drops files as ransom note. It avoids encrypting files with the following file extensions.

  TECHNICAL DETAILS

Payload:

Disables AV, Encrypts 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 adds the following processes:

  • /c del c:\{Malware File Path}>>NUL

Process Termination

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

  • MySQL
  • MySQL80
  • SQLSERVERAGENT
  • MSSQLSERVER
  • SQLWriter
  • SQLTELEMETRY
  • MSDTC
  • SQLBrowser
  • vmcompute
  • vmms
  • MSExchangeUMCR
  • MSExchangeUM
  • MSExchangeTransportLogSearch
  • MSExchangeTransport
  • MSExchangeThrottling
  • MSExchangeSubmission
  • MSExchangeServiceHost
  • MSExchangeRPC
  • MSExchangeRepl
  • MSExchangePOP3BE
  • MSExchangePop3
  • MSExchangeNotificationsBroker
  • MSExchangeMailboxReplication
  • MSExchangeMailboxAssistants
  • MSExchangeIS
  • MSExchangeIMAP4BE
  • MSExchangeImap4
  • MSExchangeHMRecovery
  • MSExchangeHM
  • MSExchangeFrontEndTransport
  • MSExchangeFastSearch
  • MSExchangeEdgeSync
  • MSExchangeDiagnostics
  • MSExchangeDelivery
  • MSExchangeDagMgmt
  • MSExchangeCompliance
  • MSExchangeAntispamUpdate

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

  • sqlagent.exe
  • sqlservr.exe
  • sqlwriter.exe
  • sqlceip.exe
  • msdtc.exe
  • sqlbrowser.exe
  • vmwp.exe
  • vmsp.exe
  • outlook.exe
  • Microsoft.Exchange.Store.Worker.exe

Other Details

This Ransomware does the following:

  • It terimnates if the machine supports the following system language:
    • Russian
  • It only encrypts local volumes with size larger than 1GB
  • Files are encrypted in 1 MB chunks, and the number of bytes skipped depends on the file's size.
    • File Size: Less than 2 MB
      • Chunk Size: All the file content
      • Skipped Size: 0 MB
    • File Size: Less than 10 MB
      • Chunk Size: 1 MB
      • Skipped Size: 4 MB
    • File Size: Less than 50 MB
      • Chunk Size: 1 MB
      • Skipped Size: 8 MB
    • File Size: Less than 200 MB
      • Chunk Size: 1 MB
      • Skipped Size: 16 MB
    • File Size: Less than 10 GB
      • Chunk Size: 1 MB
      • Skipped Size: 200 MB
    • File Size: More than 10 GB
      • Chunk Size: 1 MB
      • Skipped Size: 500 MB

    It accepts the following parameters:

    • network - retrieves address resolution protocol
    • local - Encrypts every local volume in the machine
    • {Target Path} - Encrypts the specified path
    • {Target IP} - Encrypts the specified IP Address

    Ransomware Routine

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

    • \windows\
    • \program files\microsoft office\
    • \program files (x86)\microsoft office\
    • \program files\avs\
    • \program files (x86)\avs\
    • \$recycle.bin\
    • \boot\
    • \recovery\
    • \system volume information\
    • \msocache\
    • \users\all users\
    • \users\default user\
    • \users\default\
    • \temp\
    • \inetcache\
    • \google\

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

    • .cuba

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

    • {Encrypted Directory}\!! READ ME !!.txt

    It avoids encrypting files with the following file extensions:

    • .exe
    • .dll
    • .sys
    • .ini
    • .lnk
    • .vbm
    • .cuba

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

18.710.02

FIRST VSAPI PATTERN DATE:

21 Sep 2023

VSAPI OPR PATTERN File:

18.711.00

VSAPI OPR PATTERN Date:

22 Sep 2023

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:

    • ADW.Win32.TRX.XXPE50FFF072

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}\!! READ ME !!.txt

Step 5

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