The Exitium (.exitium) Ransomware Recovery and Decryption Options

In our recovery lab today at Lockbit Decryptor, we isolated the Exitium ransomware strain. Our analysis confirms this is not a sophisticated enterprise threat but a variant of the open-source Chaos ransomware. This variant uses a stream cipher with a hard-coded key and appends the .exitium extension. Despite its threatening ransom note and strict deadlines, the encryption is fundamentally broken and allows for complete file recovery without any actor interaction.

Latest: The MedusaLocker (“.bear”) Variants: A Definitive Forensic Recovery Guide

EMERGENCY TRIAGE (THE GOLDEN HOUR)

If you are observing the .exitium extension on your systems, execute these 4 steps immediately:

1. Network Segmentation: Immediately sever all SMB (TCP 445) and RDP (TCP 3389) connections to prevent the simple script from spreading to other accessible shares.
2. Process Termination: Identify and terminate the ransomware process. It is often a single .exe file with a randomized name running under the user’s context.
3. Malware Removal: Scan the affected system with a reputable antivirus solution to remove the initial dropper and any secondary payloads.
4. Block Tox Traffic: Restrict outbound traffic to prevent employees from installing the qTox client and communicating with the threat actors via their specified Tox ID.

Also read: The PCLocked ‘.pclocked’ Variant: A Definitive Forensic Recovery Guide

THREAT PROFILE & FORENSICS

Technical Specifications:

File Extension Examples:

• database.sql.exitium
• report.pdf.exitium
• financial.xlsx.exitium
• image.jpg.exitium
• document.docx.exitium

Persistence Markers:

• Windows Registry: The malware may establish persistence via HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\{Random_GUID}.
• Startup Folder: A copy of the executable may be placed in the user’s Startup folder (%APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup).
• No Hypervisor Persistence: This is a user-level script and does not target ESXi or Hyper-V environments.

Ransom Note Text:

----------------------------------------------------
Hello, Management!
Files from your infra have been encrypted by Exitium ransomware!

All data, including passports, IDs, employes, healthcare and other data has been encrypted and can be lost irrevocable!
CONTACT US WITHIN 168 HOURS OR YOUR FILES WILL STAY ENCRYPTED FOREVER
NO NEED TO TRY DELETE OR MODIFY ENCRYPTED FILES!
THIS WILL LEAD TO IMPOSSIBILITY OF FILE DECRYPTION

How to contact us:
1. Download Tox here - hxxps://github.com/TokTok/qTox/releases/download/v1.18.3/setup-qtox-x86_64-release.exe
2. Go to 'Add Friend' and send request to this TOX_ID: 0932023CDBDC780B80B4772D22975C9AAD6D1A5921AA4C746C9E4851A307DE1888A6F56FDFBE
3. After you contact us we will start negotiations
...
OUR BLOG(Tor link): -
----------------------------------------------------

MATHEMATICAL VULNERABILITY ANALYSIS

The Exitium variant uses a simple stream cipher for encryption. The encryption process for a plaintext byte $P_i$ and a key byte $K_j$ is:

$$C_i = P_i \oplus K_j$$

Where $C_i$ is the ciphertext byte and the key $K_j$ is repeated cyclically.

Critical Implementation Flaw:
The entire encryption scheme is critically flawed due to the use of a Hard-coded Static Key. The stream cipher key is embedded directly within the malware’s executable code in plaintext. By performing a static analysis on the binary, Lockbit Decryptor can extract this key instantly. Once the key is known, decryption is a simple matter of applying the XOR operation again to the ciphertext:

$$P_i = C_i \oplus K_j$$

This allows for the complete and instantaneous recovery of all encrypted files. In some Chaos variants, the encryption is so flawed that files are merely corrupted and not encrypted at all, allowing for manual restoration by removing the extension.

IT ADMIN TOOLKIT (POWERSHELL AUDIT)

Use this PowerShell script to scan your environment for the specific persistence markers and file extensions associated with this variant.

# Lockbit Decryptor Audit Script for Exitium Variant
Write-Host "Scanning for .exitium Persistence..." -ForegroundColor Cyan

# 1. Audit Registry Run Keys for Suspicious Entries
Get-ItemProperty -Path "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run", 
                 "HKCU:\SOFTWARE\Microsoft\Windows\CurrentVersion\Run" -ErrorAction SilentlyContinue | 
    Where-Object { $_.PSObject.Properties.Value -match "%TEMP%|%APPDATA%" } | 
    Select-Object PSPath, @{N="SuspiciousValue";E={$_.PSObject.Properties.Value}}

# 2. Scan for .exitium Extensions and Ransom Notes
Get-ChildItem -Path "C:\" -Filter "*.exitium" -Recurse -ErrorAction SilentlyContinue -Depth 3 | 
    Select-Object FullName, Length, CreationTime

Get-ChildItem -Path "C:\" -Filter "YOU ARE UNDER ATTACK!.html" -Recurse -ErrorAction SilentlyContinue -Depth 3 | 
    Select-Object FullName, CreationTime

RECOVERY PATHWAYS & CTA

Recovery Options:

• Professional Key Extraction & Decryption: Lockbit Decryptor can extract the static stream cipher key from the malware binary and use it to decrypt all files instantly.
• Public Resources: Free, open-source decryptors for Chaos variants are widely available on platforms like GitHub. Any tool capable of analyzing the binary can extract the key.
• Manual File Restoration: For some Chaos builds, simply removing the .exitium extension may be enough to restore file functionality, as the encryption process may have failed.
• Final Recommendation: Do not contact the actors via Tox. This is a low-skill attack using a well-known, broken encryption scheme. Their threats of permanent data loss are baseless. Paying is unnecessary. Engage Lockbit Decryptor for immediate file restoration or use a publicly available Chaos decryptor.

Also read: The Uragan (.uragan) Variant: A Definitive Forensic Recovery Guide

Frequently Asked Questions (FAQ)

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