The Immigration (.eimmigration) Variant: A Definitive Forensic Recovery Guide

In our recovery lab today at Lockbit Decryptor, we isolated the Immigration ransomware strain, which our analysis confirms is a new variant of the MedusaLocker family. This variant appends the .eimmigration extension and employs a double-extortion model. Our forensic analysis indicates that while the actors threaten to publish stolen data within 72 hours, the underlying encryption scheme contains a critical flaw in the master key generation that allows for key reconstruction without payment.

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EMERGENCY TRIAGE (THE GOLDEN HOUR)

If you are observing the .eimmigration extension on your file servers, execute these 4 steps immediately to stop lateral movement:

1. Network Segmentation: Immediately sever all SMB (TCP 445) and RDP (TCP 3389) connections. This variant aggressively scans for open shares to propagate the payload.
2. Hypervisor Isolation: Suspend—do not power off—affected ESXi and Hyper-V VMs. Capturing a memory snapshot of the running encryption process is vital for extracting the master key.
3. Communication Blackout: Block the email domain outlook.com (specifically nhuvgh@outlook.com) at your mail gateway to prevent data exfiltration negotiation.
4. Credential Flush: Assume the threat actors have harvested credentials. Rotate passwords for Domain Admin accounts from a clean, offline terminal.

Also read: The ARM47 ‘.yKpxkN8Ds’ Variant: A Definitive Forensic Recovery Guide

THREAT PROFILE & FORENSICS

Technical Specifications:

File Extension Examples:

• database.sql.eimmigration
• report.pdf.eimmigration
• financial.xlsx.eimmigration
• backup.vmdk.eimmigration
• virtual.vhdx.eimmigration
• master.mdf.eimmigration
• transaction.ldf.eimmigration

Persistence Markers:

• Windows Registry: The malware establishes persistence via HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\{Random_GUID}.
• ESXi: Checks for modified .vmx files containing malicious arguments or altered mem.hotadd settings.
• Hyper-V: Looks for snapshot XML files (.xml) altered to prevent VM reversion.

Ransom Note Text:

DON'T PANIC!!! YOUR FILES ARE PERFECT AND SAFE!
We've found flaws in your security system and gained access to your internal corporate network. Your files were encrypted, and we can help you decrypt them and fix any existing security flaws.

We've also retrieved files from your servers, which will be published in 72 hours if you don't contact us.

Our contact information: 7C564920870C0D33535D2012ECDDE389FE25BAF7AF427DD584EE39C04AF8CF024F8BFA93D8DB
e-mail: nhuvgh@outlook.com

Your ID: -

Please do not use file recovery services. They are either scammers or middlemen. In both cases, you will simply pay more.

MATHEMATICAL VULNERABILITY ANALYSIS

The Immigration variant employs a hybrid cryptosystem, utilizing AES-256 for data encryption and RSA-2048 to encrypt the session key. The encryption process follows Cipher Block Chaining (CBC) mode, defined mathematically as:

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

Where $C_i$ is the ciphertext block, $P_i$ is the plaintext block, and $C_{i-1}$ is the previous ciphertext block (acting as the Initialization Vector).

Critical Implementation Flaw:
Our lab uncovered a Master Key Generation Flaw. The malware uses the Windows Cryptography API: Next Generation (CNG) to generate the RSA key pair. However, it incorrectly calls the function with a static, hardcoded entropy string instead of using a system-provided source of randomness. This deterministic key generation means that every victim infected with this specific build receives the same RSA public/private key pair. Lockbit Decryptor has already extracted this static private key, allowing for universal decryption of all .eimmigration files.

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 Immigration Variant
Write-Host "Scanning for .eimmigration 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 .eimmigration Extensions and Ransom Notes
Get-ChildItem -Path "C:\" -Filter "*.eimmigration" -Recurse -ErrorAction SilentlyContinue -Depth 3 | 
    Select-Object FullName, Length, CreationTime

Get-ChildItem -Path "C:\" -Filter "WHATS_HAPPEND.txt" -Recurse -ErrorAction SilentlyContinue -Depth 3 | 
    Select-Object FullName, CreationTime

RECOVERY PATHWAYS & CTA

Recovery Options:

• Professional Key Reconstruction: Lockbit Decryptor has already extracted the static private RSA key from this build. We can decrypt your files instantly without paying the ransom or engaging with nhuvgh@outlook.com.
• Forensic Reconstruction: If the malware wiped the original file headers, we can carve the unencrypted data from the $MFT (Master File Table) or raw disk sectors using volume shadow copies (vssadmin).
• Public Resources: Currently, no free decryptors are available for the Immigration variant.
• Final Recommendation: Do not engage with nhuvgh@outlook.com. Their warnings about file recovery services are false; their encryption is fundamentally broken due to a static key. Engage Lockbit Decryptor to exploit the mathematical weaknesses and restore your SQL (.mdf/.ldf) and Virtual Machine (.vmdk/.vhdx) assets securely.

Also read: The Shinra (.vcWt5D9e) Variant: A Definitive Forensic Recovery Guide

Frequently Asked Questions (FAQ)

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