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Ransom.MSIL.KARSOVROP.A

January 05, 2024
 Analysis by: John Rainier Navato
 ALIASES:

UDS:Trojan-Ransom.MSIL.Encoder.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 drops files as ransom note. It avoids encrypting files with the following file extensions.

  TECHNICAL DETAILS

File Size:

28,609 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

02 Jan 2024

Payload:

Drops files, Terminates processes, 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 adds the following processes:

  • "cmd.exe" /c net stop wscsvc
  • "%System%\vssadmin.exe" delete shadows /all /quite
  • "cmd.exe" /c {Malware File Path}\DeleteItself.bat

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

Process Termination

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

  • agntsvc
  • dbeng50
  • dbsnmp
  • encsvc
  • excel
  • firefoxconfig
  • infopath
  • isqlplussvc
  • msaccess
  • msftesql
  • mspub
  • mydesktopqos
  • mydesktopservice
  • mysqld
  • mysqld-nt
  • mysqld-opt
  • ocautoupds
  • ocomm
  • ocssd
  • onenote
  • oracle
  • outlook
  • powerpnt
  • sqbcoreservice
  • sqlagent
  • sqlbrowser
  • sqlservr
  • sqlwriter
  • steam
  • synctime
  • tbirdconfig
  • thebat
  • thebat64
  • thunderbird
  • visio
  • winword
  • wordpad
  • xfssvccon
  • Any process whose image path does not start in %System Root%
  • Any process whose image path does not contain "microsoft" or "windows" (case-insensitive)

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

Dropping Routine

This Ransomware drops the following files:

  • {Encrypted Path}\{Encrypted File Name}.{Encrypted File Extension}.karsovrop_TMP → deleted after the file is encrypted
  • {Malware File Path}\DeleteItself.bat → used to delete the malware (deleted afterwards)

Other Details

This Ransomware does the following:

  • It will only execute if the system date is after the 15th of every month from the year 2024 onwards.
  • It avoids encrypting files that contains the following strings at the end of their filenames:
    • FILE RECOVERY.txt
  • It shows the following dialog box which accepts the path/directory to prioritize in encrypting:

Ransomware Routine

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

  • autorun.inf
  • boot.ini
  • Bootfont.bin
  • bootsect.bak
  • concache.db
  • DECRYPT-FILES.html
  • desktop.ini
  • io.sys
  • ntdetect.com
  • ntldr
  • ntuser.dat
  • ntuser.dat.log
  • readme-warning.txt
  • thumbs.db

It avoids encrypting files found in the following folders:

  • $windows.~bt
  • $windows.~ws
  • appdata
  • application data
  • Assemblies
  • boot
  • Common Files
  • Core Runtime
  • google
  • intel
  • Internet Explorer
  • Microsoft Analysis Services
  • Microsoft ASP.NET
  • Microsoft Help Viewer
  • Microsoft MPI
  • Microsoft Security Client
  • Microsoft Security Client
  • Microsoft.NET
  • mozilla
  • msocache
  • Package
  • Package Store
  • perflogs
  • programdata
  • Reference
  • Store
  • system volume information
  • tor browser
  • Windows
  • Windows Defender
  • Windows Kits
  • Windows Mail
  • Windows Microsoft.NET
  • Windows NT
  • Windows Photo Viewer
  • Windows Portable Devices
  • Windows Sidebar
  • windows.old
  • WindowsPowerShell

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

  • .karsovrop

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

  • {Discovered Path}\FILE RECOVERY.txt

It avoids encrypting files with the following file extensions:

  • .386
  • .adv
  • .ani
  • .bat
  • .bin
  • .cab
  • .cmd
  • .com
  • .cpl
  • .cur
  • .deskthemepack
  • .diagcab
  • .diagpkg
  • .dll
  • .drv
  • .exe
  • .hlp
  • .hta
  • .icl
  • .icns
  • .ico
  • .ics
  • .idx
  • .jar
  • .karsovrop
  • .karsovrop_TMP
  • .lnk
  • .mod
  • .mpa
  • .msc
  • .msi
  • .msp
  • .msstyles
  • .msu
  • .nls
  • .nomedia
  • .ocs
  • .prf
  • .ps1
  • .rom
  • .rtp
  • .scr
  • .shs
  • .sys
  • .theme
  • .themepack
  • .wpx

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

18.920.04

FIRST VSAPI PATTERN DATE:

04 Jan 2024

VSAPI OPR PATTERN File:

18.921.00

VSAPI OPR PATTERN Date:

05 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.XXPE50FFF075

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 Path}\{Encrypted File Name}.{Encrypted File Extension}.karsovrop_TMP
  • {Malware File Path}\DeleteItself.bat

Step 5

Scan your computer with your Trend Micro product to delete files detected as Ransom.MSIL.KARSOVROP.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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