Analysis by: Jeffrey Francis Bonaobra
ALIASES:

Ransom:Win32/BlackCat.A (MICROSOFT), BScope.TrojanRansom.BlackCat (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: 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.

  TECHNICAL DETAILS

File Size: 12344320 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 18 Mar 2023
Payload: Drops files, Modifies system registry, Displays graphics/image, Terminates processes, Disables AV, 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 files:

  • %Desktop%\RECOVER-7xdxxdp-FILES.txt.png → used to change wallpaper

(Note: %Desktop% is the current user's desktop, which is usually C:\Documents and Settings\{User Name}\Desktop on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\Desktop on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It adds the following processes:

  • "%System%\cmd.exe" /c "iisreset.exe /stop"
  • "%System%\cmd.exe" /c "reg add HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters /v MaxMpxCt /d 65535 /t REG_DWORD /f"
  • "{Malware File Path}\{Malware File Name}" --child --access-token {ACCESS_TOKEN} → Executed multiple times
  • "%System%\cmd.exe" /c "vssadmin.exe Delete Shadows /all quiet"
  • "%System%\cmd.exe" /c arp -a
  • "%System%\cmd.exe" /c "wmic.exe Shadowcopy Delete"
  • "%System%\cmd.exe" /c bcdedit set {default} recoveryenabled No
  • "%System%\cmd.exe" /c "wevtutil.exe el"
  • "%System%\cmd.exe" /c "wevutil.exe cl \"{Windows Event Logs}"
  • "%System%\cmd.exe" /c fsutil behavior set SymlinkEvaluation R2R:1
  • "%System%\cmd.exe" /c fsutil behavior set SymlinkEvaluation R2L:1
  • wmic csproduct get UUID
  • "powershell.exe -encodedCommand {Base 64 encoded command} → used to terminate services that has "sql" in its name
  • bcdedit /c set {current} safeboot minimal → if the --safeboot parameter is used
  • bcdedit /c set {current} safeboot network → if the --safeboot-network parameter is used
  • bcdedit /c deletevalue {current} safeboot

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

Autostart Technique

This Ransomware adds the following entries to allow itself to run on safe mode:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\3969357994888896545222593337177876501
ImagePath = {Malware File Path}\{Malware File Name} --access-token {ACCESS_TOKEN} --prop-arg-safeboot --safeboot-entry --no-net --no-prop --no-impers → if --safeboot parameter is used

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\3969357994888896545222593337177876501
ImagePath = {Malware File Path}\{Malware File Name} --access-token {ACCESS_TOKEN} --prop-arg-safeboot-network --safeboot-entry → if --safeboot-network parameter is used

Other System Modifications

This Ransomware adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\LanmanServer\Parameters
MaxMpxCt = 65535

It changes the desktop wallpaper by modifying the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = %Desktop%\RECOVER-7xdxxdp-FILES.txt.png

It sets the system's desktop wallpaper to the following image:

  • %Desktop%\RECOVER-7xdxxdp-FILES.txt.png
    BlackCat Desktop Wallpaper

Process Termination

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

  • mepocs
  • memtas
  • veeam
  • svc$
  • backup
  • sql
  • vss
  • msexchange
  • sql$
  • mysql
  • mysql$
  • sophos
  • MSExchange
  • MSExchange$
  • WSBExchange
  • PDVFSService
  • BackupExecVSSProvider
  • BackupExecAgentAccelerator
  • BackupExecAgentBrowser
  • BackupExecDiveciMediaService
  • BackupExecJobEngine
  • BackupExecManagementService
  • BackupExecRPCService
  • GxBlr
  • GxVss
  • GxClMgrS
  • GxCVD
  • GxCIMgr
  • GXMMM
  • GxVssHWProv
  • GxFWD
  • SAPService
  • SAP
  • SAP$
  • SAPD$
  • SAPHostControl
  • SAPHostExec
  • QBCFMonitorService
  • QBDBMgrN
  • QBIDPService
  • AcronisAgent
  • VeeamNFSSvc
  • VeeamDeploymentService
  • VeeamTransportSvc
  • MVArmor
  • MVarmor64
  • VSNAPVSS
  • AcrSch2Svc
  • services that has "sql" in its name

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

  • agntsvc
  • dbeng50
  • dbsnmp
  • encsvc
  • excel
  • firefox
  • infopath
  • isqlplussvc
  • msaccess
  • mspub
  • mydesktopqos
  • mydesktopservice
  • notepad
  • ocautoupds
  • ocomm
  • ocssd
  • onenote
  • oracle
  • outlook
  • powerpnt
  • sqbcoreservice
  • sql
  • steam
  • synctime
  • tbirdconfig
  • thebat
  • thunderbird
  • visio
  • winword
  • wordpad
  • xfssvccon
  • *sql*
  • bedbh
  • vxmon
  • benetns
  • bengien
  • pvlsvr
  • beserver
  • raw_agent_svc
  • vsnapvss
  • CagService
  • QBIDPService
  • QBDBMgrN
  • QBCFMonitorService
  • SAP
  • TeamViewer_Service
  • TeamViewer
  • tv_w32
  • tv_x64
  • CVMountd
  • cvd
  • cvfwd
  • CVODS
  • saphostexec
  • saposcol
  • sapstartsrv
  • avagent
  • avscc
  • DellSystemDetect
  • EnterpriseClient
  • VeeamNFSSvc
  • VeeamTransportSvc
  • VeeamDeploymentSvc

Other Details

This Ransomware does the following:

  • It terminates ESXi VMs.
  • It clears event logs
  • It uses PsExec to propagate.

It accepts the following parameters:

  • --access-token {ACCESS_TOKEN} → Access Token
  • --drag-and-drop → Invoked with drag and dropped
  • --drop-drag-and-drop-target → Drop drag and drop target batch file
  • --extra-verbose → Log more to console
  • -h, --help → Print help information
  • --log-file {LOG_FILE} → Enable logging to specified file
  • --no-impers → Do not spawn impersonated processes on Windows
  • --no-net → Do not discover network shares on Windows
  • --no-prop → Do not self propagate on Windows
  • --no-prop-servers {NO_PROP_SERVERS} → Do not propagate to defined servers
  • --no-vm-kill → Do not stop VMs on ESXi
  • --no-vm-kill-names {NO_VM_KILL_NAMES} → Do not stop defined VMs on ESXi
  • --no-vm-snapshot-kill → Do not wipe VMs snapshots on ESXi
  • --no-wall → Do not update desktop wallpaper on Windows
  • -p, --path {PATHS} → Only process files inside defined paths
  • --prop-file {PROP_FILE} → Propagate specified file
  • --safeboot → Reboot in safe mode before running on Windows
  • --safeboot-instance → Run as safeboot instance on Windows
  • --safeboot-network → Reboot in safe mode with networking before running on Windows
  • --sleep-restart {SLEEP_RESTART} → Sleep for duration in seconds after successful run and then restart. This is soft persistence, keeps process alive no longer than defined in --sleep-restart duration, 24 hours by default.
  • --sleep-restart-duration {SLEEP_RESTART_DURATION} → Keep soft persistence alive for duration in seconds. 24 hours by default.
  • --sleep-restart-until {SLEEP_RESTART_UNTIL} → Keep soft persistence alive until defined UTC time in millis. Defaults to 24 hours since launch.
  • --ui → Show user interface
  • -v, --verbose → Log to console

Ransomware Routine

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

  • File Extensions:
    • .deskthemepack
    • .dll
    • .drv
    • .exe
    • .lnk
    • .lock
    • .msc
    • .msstyles
    • .msu
    • .sys
    • .theme
    • .themepack
  • File Names:
    • NTUSER.DAT
    • autorun.inf
    • boot.ini
    • desktop.ini
  • Directories:
    • \$windows.~bt
    • \$windows.~ws
    • \AppData\Local\Microsoft\GameDVR
    • \AppData\Local\Microsoft\Internet Explorer
    • \AppData\Local\Packages\Microsoft
    • \AppData\Local\Packages\MicrosoftWindows
    • \Boot
    • \PerfLogs
    • \Program Files (x86)\*Edge*
    • \Program Files (x86)\Common Files
    • \Program Files (x86)\Common Files\Microsoft Shared
    • \Program Files (x86)\Common Files\Services
    • \Program Files (x86)\Common Files\System
    • \Program Files (x86)\Internet Explorer
    • \Program Files (x86)\Microsoft.NET
    • \Program Files (x86)\Microsoft\*Edge*
    • \Program Files (x86)\Microsoft\Temp
    • \Program Files (x86)\Windows Defender
    • \Program Files (x86)\Windows Mail
    • \Program Files (x86)\Windows Media Player
    • \Program Files (x86)\Windows Multimedia Platform
    • \Program Files (x86)\Windows NT
    • \Program Files (x86)\Windows Photo Viewer
    • \Program Files (x86)\Windows Portable Devices
    • \Program Files (x86)\Windows Security
    • \Program Files (x86)\Windows Sidebar
    • \Program Files (x86)\WindowsPowerShell
    • \Program Files\Common Files\microsoft shared
    • \Program Files\Common Files\Services
    • \Program Files\Common Files\System
    • \Program Files\Internet Explorer
    • \Program Files\ModifiableWindowsApps
    • \Program Files\Uninstall Information
    • \Program Files\Windows Defender
    • \Program Files\Windows Mail
    • \Program Files\Windows Media Player
    • \Program Files\Windows NT
    • \Program Files\Windows Photo Viewer
    • \Program Files\Windows Portable Devices
    • \Program Files\Windows Security
    • \Program Files\Windows Sidebar
    • \Program Files\WindowsApps
    • \Program Files\WindowsPowerShell
    • \ProgramData\Microsoft\Device Stage
    • \ProgramData\Microsoft\DeviceSync
    • \ProgramData\Microsoft\Diagnosis
    • \ProgramData\Microsoft\DiagnosticLogCSP
    • \ProgramData\Microsoft\DRM
    • \ProgramData\Microsoft\EdgeUpdate
    • \ProgramData\Microsoft\Event Viewer
    • \ProgramData\Microsoft\IdentityCRL
    • \ProgramData\Microsoft\MapData
    • \ProgramData\Microsoft\MF
    • \ProgramData\Microsoft\NetFramework
    • \ProgramData\Microsoft\Network
    • \ProgramData\Microsoft\Provisioning
    • \ProgramData\Microsoft\Search
    • \ProgramData\Microsoft\SmsRouter
    • \ProgramData\Microsoft\Spectrum
    • \ProgramData\Microsoft\Speech_OneCore
    • \ProgramData\Microsoft\Storage Health
    • \ProgramData\Microsoft\User Account Pictures
    • \ProgramData\Microsoft\Vault
    • \ProgramData\Microsoft\WDF
    • \ProgramData\Microsoft\Windows
    • \ProgramData\Microsoft\Windows Defender
    • \ProgramData\Microsoft\Windows NT
    • \ProgramData\Microsoft\Windows Security Health
    • \ProgramData\Microsoft\WinMSIPC
    • \ProgramData\Microsoft\WPD
    • \ProgramData\Packages\Microsoft
    • \ProgramData\Packages\MicrosoftWindows
    • \ProgramData\Packages\USOPrivate
    • \ProgramData\Packages\USOShared
    • \ProgramData\Packages\WindowsHolographicDevices
    • \ProgramData\ssh\
    • \ProgramData\USOPrivate
    • \ProgramData\USOShared
    • \windows
    • \windows.old

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

  • .7xdxxdp

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

  • {Encrypted Directory}\RECOVER-7xdxxdp-FILES.txt
  • %Desktop%\RECOVER-7xdxxdp-FILES.txt
    BlackCat Ransom Note

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 18.336.02
FIRST VSAPI PATTERN DATE: 23 Mar 2023
VSAPI OPR PATTERN File: 18.337.00
VSAPI OPR PATTERN Date: 24 Mar 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:

     
    • Troj.Win32.TRX.XXPE50FFF066

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

Delete this registry value

[ 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.

  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\3969357994888896545222593337177876501
    • ImagePath = {Malware File Path}\{Malware File Name} --access-token {ACCESS_TOKEN} --prop-arg-safeboot --safeboot-entry --no-net --no-prop --no-impers
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\3969357994888896545222593337177876501
    • ImagePath = {Malware File Path}\{Malware File Name} --access-token {ACCESS_TOKEN} --prop-arg-safeboot-network --safeboot-entry
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters
    • MaxMpxCt = 65535
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • Wallpaper = %Desktop%\RECOVER-7xdxxdp-FILES.txt.png

Step 6

Disable this malware service

[ Learn More ]
    • Service Name: 3969357994888896545222593337177876501
    • Image Path: {Malware File Path}\{Malware File Name} --access-token {ACCESS_TOKEN} --prop-arg-safeboot --safeboot-entry --no-net --no-prop --no-impers
    • Service Name: 3969357994888896545222593337177876501
    • Image Path: {Malware File Path}\{Malware File Name} --access-token {ACCESS_TOKEN} --prop-arg-safeboot-network --safeboot-entry

Step 7

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.
  • %Desktop%\RECOVER-7xdxxdp-FILES.txt.png
  • {Encrypted Directory}\RECOVER-7xdxxdp-FILES.txt
  • %Desktop%\RECOVER-7xdxxdp-FILES.txt

Step 8

Reset your Desktop properties

[ Learn More ]

Step 9

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win32.BLACKCAT.D. 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 10

Restore encrypted files from backup.


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