Ransom.Win64.TENGU.TCLRYNAA.go

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 does not have any propagation routine.

It does not have any backdoor routine.

It does not have any information-stealing capability.

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

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:

• %User Temp%\Wallpaper.png → Embedded ransom wallpaper (deleted after applying to desktop/lock screen)
  

It adds the following processes:

• wmic shadowcopy delete
• wmic service where name='vss' call ChangeStartMode Disabled
• net stop vss

It adds the following mutexes to ensure that only one of its copies runs at any one time:

• locker_mutex.lock

Other System Modifications

This Ransomware adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\PersonalizationCSP
LockScreenImagePath = %User Temp%\Wallpaper.png

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\PersonalizationCSP
LockScreenImageStatus = 1

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows\Personalization
LockScreenImage = %User Temp%\Wallpaper.png

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Authentication\
LogonUI\Background
OEMBackground = 1

(Note: The default value data of the said registry entry is 0.)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = %User Temp%\Wallpaper.png

(Note: The default value data of the said registry entry is {Default wallpaper image}.)

Propagation

This Ransomware does not have any propagation routine.

Backdoor Routine

This Ransomware does not have any backdoor routine.

Rootkit Capabilities

This Ransomware does not have rootkit capabilities.

Process Termination

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

• vss
• sql
• svc$
• memtas
• mepocs
• msexchange
• sophos
• veeam
• backup
• GxVss
• GxBlr
• GxFWD
• GxCVD
• GxCIMgr

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

• sql
• oracle
• ocssd
• dbsnmp
• synctime
• agntsvc
• isqlplussvc
• xfssvccon
• mydesktopservice
• ocautoupds
• encsvc
• firefox
• tbirdconfig
• mydesktopqos
• ocomm
• dbeng50
• sqbcoreservice
• excel
• infopath
• msaccess
• mspub
• onenote
• outlook
• powerpnt
• steam
• thebat
• thunderbird
• visio
• winword
• wordpad
• notepad
• calc
• wuauclt
• onedrive

Information Theft

This Ransomware does not have any information-stealing capability.

Other Details

This Ransomware does the following:

• Disables Windows Spotlight feature to ensure ransom note wallpaper persistence.

It accepts the following parameters:

• --spread {file} → Enable lateral movement with host list file
• --paths → Colon-separated list of specific paths to encrypt
• --ips → Target IP addresses for network propagation
• --logs → Log file path for operator debugging
• --no-wallpaper → Suppress wallpaper and lock screen modifications
• -no-admin → Skip administrator privilege checks
• bg → Launch background worker mode for scripted deployment

It does not exploit any vulnerability.

Ransomware Routine

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

• autoexec.bat
• bootfont.bin
• bootsect.bak
• iconcache.db
• d3d9caps.dat
• desktop.ini
• autorun.inf
• config.sys
• ntuser.dat
• ntuser.ini
• config.msi
• boot.ini
• logs.txt
• thumbs.db

It avoids encrypting files found in the following folders:

• $recycle.bin
• $windows.~bt
• $windows.~ws
• programdata
• windows.old
• tor browser
• system32
• perflogs
• msocache
• public
• .nuget
• msys64
• x64dbg

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

• .TENGU

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

• {Encrypted Directory}\_README_TENGU.txt
  

It avoids encrypting files with the following file extensions:

• .sys
• .dll
• .com
• .scr
• .bat
• .vbs
• .ps1
• .lnk
• .inf
• .reg
• .msi
• .ini
• .386
• .adv
• .ani
• .bin
• .cab
• .cmd
• .cpl
• .cur
• .drv
• .hlp
• .icl
• .ico
• .ics
• .idx
• .ldf
• .mod
• .mpa
• .msc
• .msp
• .msu
• .nls
• .ocx
• .prf
• .rom
• .rtp
• .shs
• .spl
• .wpx
• .key
• .hta
• .pdb
• .lock
• .icns
• .theme
• .themepack
• .search-ms
• .diagcab
• .diagcfg
• .diagpkg
• .nomedia