Analysis by: Francesca Villasanta
ALIASES:

UDS:Trojan.MSIL.DelShad.gen (KASPERSKY)

 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.

It adds certain registry entries to disable the Task Manager. This action prevents users from terminating the malware process, which can usually be done via the Task Manager.

It encrypts files with specific file extensions. It drops files as ransom note.

  TECHNICAL DETAILS

File Size: 294,400 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 09 Jan 2024
Payload: Drops files, Downloads files, Displays graphics/image, Modifies system registry, 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 copies of itself into the affected system:

  • %Application Data%\svchost.exe → if {Malware Path}\{Malware Filename} is not %Application Data%\svchost.exe

(Note: %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 drops the following files:

  • %User Temp%\{9 random characters}.jpg → Used as wallpaper

(Note: %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).)

It adds the following processes:

  • %Application Data%\svchost.exe → if {Malware Path}\{Malware Filename} is not %Application Data%\svchost.exe
  • "%System%\cmd.exe" /C vssadmin delete shadows /all /quiet & wmic shadowcopy delete
  • "%System%\cmd.exe" /C bcdedit /set {default} bootstatus policy ignoreallfailures & bcdedit /set {default} recoveryenabled no
  • "%System%\cmd.exe" /C wbadmin delete catalog -quiet
  • "%System%\NOTEPAD.EXE" %Application Data%\READ_ME.txt

(Note: %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).. %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 registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
UpdateTask = %Application Data%\svchost.exe

Other System Modifications

This Ransomware adds the following registry entries to disable the Task Manager:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableTaskMgr = 1

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

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = %User Temp%\{9 random characters}.jpg

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

  • %User Temp%\{9 random characters}.jpg

Propagation

This Ransomware drops copies of itself in the following drives:

  • {Available Drive aside C:}\surprise.exe

Process Termination

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

  • BackupExecAgentBrowser
  • BackupExecDiveciMediaService
  • BackupExecJobEngine
  • BackupExecManagementService
  • vss
  • sql
  • svc$
  • memtas
  • sophos
  • veeam
  • backup
  • GxVss
  • GxBlr
  • GxFWD
  • GxCVD
  • GxCIMgr
  • DefWatch
  • ccEvtMgr
  • SavRoam
  • RTVscan
  • QBFCService
  • Intuit.QuickBooks.FCS
  • YooBackup
  • YooIT
  • zhudongfangyu
  • sophos
  • stc_raw_agent
  • VSNAPVSS
  • QBCFMonitorService
  • VeeamTransportSvc
  • VeeamDeploymentService
  • VeeamNFSSvc
  • veeam
  • PDVFSService
  • BackupExecVSSProvider
  • BackupExecAgentAccelerator
  • BackupExecRPCService
  • AcrSch2Svc
  • AcronisAgent
  • CASAD2DWebSvc
  • CAARCUpdateSvc
  • TeamViewer

Other Details

This Ransomware adds the following registry keys:

HKEY_CURRENT_USER\Software\oAnWieozQPsRK7Bj83r4

It does the following:

  • It encrypts files with file size below 2,170,986,240 bytes.
  • It randomly encrypts files with file size above 2,170,986,240 bytes rendering the file unusable.
  • It displays a message box and terminates execution if any of the input languages below is detected:
    • Azerbaijan
    • Turkey

Ransomware Routine

This Ransomware encrypts files with the following extensions:

  • .txt
  • .jar
  • .dat
  • .contact
  • .settings
  • .doc
  • .docx
  • .xls
  • .xlsx
  • .ppt
  • .pptx
  • .odt
  • .jpg
  • .mka
  • .mhtml
  • .oqy
  • .png
  • .csv
  • .py
  • .sql
  • .mdb
  • .php
  • .asp
  • .aspx
  • .html
  • .htm
  • .xml
  • .psd
  • .pdf
  • .xla
  • .cub
  • .dae
  • .indd
  • .cs
  • .mp3
  • .mp4
  • .dwg
  • .zip
  • .rar
  • .mov
  • .rtf
  • .bmp
  • .mkv
  • .avi
  • .apk
  • .lnk
  • .dib
  • .dic
  • .dif
  • .divx
  • .iso
  • .7zip
  • .ace
  • .arj
  • .bz2
  • .cab
  • .gzip
  • .lzh
  • .tar
  • .jpeg
  • .xz
  • .mpeg
  • .torrent
  • .mpg
  • .core
  • .pdb
  • .ico
  • .pas
  • .db
  • .wmv
  • .swf
  • .cer
  • .bak
  • .backup
  • .accdb
  • .bay
  • .p7c
  • .exif
  • .vss
  • .raw
  • .m4a
  • .wma
  • .flv
  • .sie
  • .sum
  • .ibank
  • .wallet
  • .css
  • .js
  • .rb
  • .crt
  • .xlsm
  • .xlsb
  • .7z
  • .cpp
  • .java
  • .jpe
  • .ini
  • .blob
  • .wps
  • .docm
  • .wav
  • .3gp
  • .webm
  • .m4v
  • .amv
  • .m4p
  • .svg
  • .ods
  • .bk
  • .vdi
  • .vmdk
  • .onepkg
  • .accde
  • .jsp
  • .json
  • .gif
  • .log
  • .gz
  • .config
  • .vb
  • .m1v
  • .sln
  • .pst
  • .obj
  • .xlam
  • .djvu
  • .inc
  • .cvs
  • .dbf
  • .tbi
  • .wpd
  • .dot
  • .dotx
  • .xltx
  • .pptm
  • .potx
  • .potm
  • .pot
  • .xlw
  • .xps
  • .xsd
  • .xsf
  • .xsl
  • .kmz
  • .accdr
  • .stm
  • .accdt
  • .ppam
  • .pps
  • .ppsm
  • .1cd
  • .3ds
  • .3fr
  • .3g2
  • .accda
  • .accdc
  • .accdw
  • .adp
  • .ai
  • .ai3
  • .ai4
  • .ai5
  • .ai6
  • .ai7
  • .ai8
  • .arw
  • .ascx
  • .asm
  • .asmx
  • .avs
  • .bin
  • .cfm
  • .dbx
  • .dcm
  • .dcr
  • .pict
  • .rgbe
  • .dwt
  • .f4v
  • .exr
  • .kwm
  • .max
  • .mda
  • .mde
  • .mdf
  • .mdw
  • .mht
  • .mpv
  • .msg
  • .myi
  • .nef
  • .odc
  • .geo
  • .swift
  • .odm
  • .odp
  • .oft
  • .orf
  • .pfx
  • .p12
  • .pl
  • .pls
  • .safe
  • .tab
  • .vbs
  • .xlk
  • .xlm
  • .xlt
  • .xltm
  • .svgz
  • .slk
  • .tar.gz
  • .dmg
  • .ps
  • .psb
  • .tif
  • .rss
  • .key
  • .vob
  • .epsp
  • .dc3
  • .iff
  • .onepkg
  • .onetoc2
  • .opt
  • .p7b
  • .pam
  • .r3d

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

  • READ_ME.txt

It avoids encrypting files found in the following folders:

  • In the %System Root%:
    • Program Files
    • Program Files (x86)
    • Windows
    • $Recycle.Bin
    • MSOCache
    • Documents and Settings
    • Intel
    • PerfLogs
    • Windows.old
    • AMD
    • NVIDIA
    • ProgramData

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

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

  • .mesmerised

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

  • {Encrypted Folder}\READ_ME.txt
  • %Application Data%\READ_ME.txt

  SOLUTION

Minimum Scan Engine: 9.800
SSAPI PATTERN File: 19.102.05
SSAPI PATTERN Date: 17 Jan 2024
FIRST VSAPI PATTERN FILE: 19.103.00
FIRST VSAPI PATTERN DATE: 18 Jan 2024

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.XXPE50FFF076

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_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • UpdateTask=%Application Data%\svchost.exe
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System
    • DisableTaskMgr=1

Step 6

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.

  • In HKEY_CURRENT_USER\Software\oAnWieozQPsRK7Bj83r4

Step 7

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.
  • %Application Data%\svchost.exe
  • {Available Drive aside C}\surprise.exe
  • %User Temp%\{9 random characters}.jpg
  • {Encrypted Folder}\READ_ME.txt
  • %Application Data%\READ_ME.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.MSIL.CHAOS.H. 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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