The NBLock ‘.NBLock’ Variant: A Definitive Forensic Recovery Guide

In our recovery lab today at Lockbit Decryptor, we isolated the NBLock ransomware strain. Our analysis confirms this is not a sophisticated enterprise threat but a variant derived from the open-source Xorus ransomware builder. This variant uses AES-256 encryption but commits a catastrophic operational blunder: it saves the decryption key, albeit obfuscated, locally on the victim’s system in the key.bin file. This mistake renders the entire encryption scheme nullified and allows for complete, autonomous file recovery.

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EMERGENCY TRIAGE (THE GOLDEN HOUR)

If you discover the .NBLock extension and the README_NBLOCK.txt note, execute these 4 steps immediately:

1. Terminate Processes & Isolate Host: Open Task Manager, end any suspicious-looking processes, and physically disconnect the machine from the network to prevent further spread.
2. Locate and Preserve key.bin: IMMEDIATELY locate the key.bin file. It is typically placed in the root of each affected drive or in the user’s profile directory. Create copies of this file and store them on separate, clean media. This is your master key.
3. Quarantine Malicious Executable: Identify and quarantine the original ransomware executable that initiated the attack to prevent accidental re-execution.
4. Disable Autorun: Clean the Windows Registry Run keys and the user’s Startup folder to remove the malware’s persistence mechanisms before rebooting.

Also read: The Krybit Ransomware Decryption and Recovery Guide

THREAT PROFILE & FORENSICS

Technical Specifications:

File Extension Examples:

• database.sql.NBLock
• report.pdf.NBLock
• financial.xlsx.NBLock
• archive.zip.NBLock

Persistence Markers:

• Windows Registry: The malware establishes persistence via HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\{Random_Name}.
• Startup Folder: A shortcut to the executable is often placed in the user’s Startup folder (%APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup).
• Desktop Wallpaper Hijack: Modifies registry keys to display its custom ransom-demanding wallpaper.

Ransom Note Text:

All your files are locked with AES-256.
Do NOT delete or modify key.bin - It is your only recovery tool.
Do NOT panic, To Get your files Back To its Original form you need a decryptor which we have, Read instructions below for decryptor!
Install Tor Browser: hxxps://torproject.org/
Visit For Negotiation: -

MATHEMATICAL VULNERABILITY ANALYSIS

The NBLock variant encrypts files using AES-256 in Cipher Block Chaining (CBC) mode. The encryption process for a plaintext block $P_i$ is:

$$C_i = E_K^{AES}(P_i \oplus C_{i-1})$$

Where $K$ is the AES key and $C_{i-1}$ is the preceding ciphertext block (with the Initialization Vector, IV, acting as $C_0$).

Critical Implementation Flaw:
The fatal flaw is not in the mathematics of AES itself, but in the operational handling of the key. The malware generates a unique AES-256 key for the victim and writes it to key.bin. While this file appears scrambled, it is protected by a rudimentary, static XOR mask. The masking key is constant across all NBLock infections compiled from the same builder template. The relationship between the raw key $K$ and the stored bytes $S$ is:

$$S = K \oplus M_{static}$$

By reverse-engineering a single sample of the NBLock executable, Lockbit Decryptor extracts the static mask $M_{static}$. Applying this mask to the key.bin file retrieves the plaintext AES key $K$, granting instant decryption capabilities without any reliance on the attacker.

IT ADMIN TOOLKIT (POWERSHELL AUDIT)

Use this PowerShell script to locate the critical components of the NBLock infection.

# Lockbit Decryptor Audit Script for NBLock Variant
Write-Host "Scanning for NBLock Components..." -ForegroundColor Cyan

# 1. Scan for the Critical key.bin Files
$keyBinFiles = Get-ChildItem -Path C:\ -Name "key.bin" -Recurse -ErrorAction SilentlyContinue -Depth 3
if ($null -ne $keyBinFiles) {
    Write-Host "*** CRITICAL FINDINGS ***" -ForegroundColor Red
    foreach ($path in $keyBinFiles) {
        Write-Host "Located key.bin at: $path" -ForegroundColor Yellow
    }
} else {
    Write-Host "'key.bin' file not found in scanned locations." -ForegroundColor Gray
}


# 2. Scan for .NBLock Extensions
Get-ChildItem -Path "C:\" -Filter "*.NBLock" -Recurse -ErrorAction SilentlyContinue -Depth 3 | 
    Measure-Object | Select-Object Count

# 3. Scan for Ransom Notes
Get-ChildItem -Path "C:\" -Filter "README_NBLOCK.txt" -Recurse -ErrorAction SilentlyContinue -Depth 3 | 
    Select-Object FullName, CreationTime

RECOVERY PATHWAYS & CTA

Guaranteed Recovery Methods:

• Self-Decryption Using Local Key: This is the preferred path. Retrieve the key.bin file. Lockbit Decryptor can provide a utility that takes this file as input, removes the static XOR mask, and outputs the correct AES key, which can then be plugged into a generic AES-decryptor to restore all files.
• Professional Automated Recovery: Submit the key.bin file and a few sample encrypted files to Lockbit Decryptor. We will automate the key extraction and perform the bulk decryption for you, ensuring accuracy and speed for large datasets.
• Ignore the Actors: There is no logical reason to contact the attackers via their undisclosed Tor site. They hold no advantage over you, as the decryption instrument is already in your possession.
• Final Recommendation: Do not waste time investigating the Tor site or considering payment. The authors of NBLock have inadvertently given you the keys to your own kingdom. The priority is to safely extract the AES key from key.bin. Contact Lockbit Decryptor for immediate assistance in developing a tailored decryptor from your local key file to seamlessly restore your SQL (.mdf), document, and multimedia files.

Also read: The Shinra v3 (.qPUvslnc) Variant: A Definitive Forensic Recovery Guide

Frequently Asked Questions (FAQ)

Contact Us To Purchase The NBLock Decryptor Tool