1. Executive Summary: The Rust-Based MedusaLocker3 Threat

The ransomware landscape is currently undergoing a massive architectural evolution, with veteran syndicates migrating away from legacy frameworks to modern, cross-platform languages. Discovered in late 2026, the .CHUNGACHANGA ransomware is a highly sophisticated, high-speed variant of the MedusaLocker3 (Version 5) family. Entirely rewritten in Rust, this variant is engineered for maximum execution speed, deep evasion of traditional antivirus signatures, and catastrophic disruption of enterprise networks.

Upon breaching a corporate network, the MedusaLocker3 payload rapidly traverses local drives, mapped network shares, and centralized storage. It encrypts mission-critical data, appending the highly unusual .CHUNGACHANGA extension to all impacted files. A primary database originally named inventory.mdf is instantly rendered useless as inventory.mdf.CHUNGACHANGA.

A distinct forensic marker of these newer Rust-based MedusaLocker variants is the extremely long, 1618-character hexadecimal “Key ID” embedded at the top of their RANSOM_NOTE.html files. The attackers utilize a strict double-extortion model, exfiltrating sensitive corporate data prior to encryption and threatening to leak it online if a ransom is not paid within a 72-hour window. This playbook provides IT administrators, network engineers, and incident responders with a clear roadmap to contain the active breach, audit the damage, and navigate the high-stakes extortion threat orchestrated via ProtonMail addresses like [email protected].

2. Threat Intelligence & Technical Specifications

To successfully counter a MedusaLocker3 deployment, defenders must understand the adversary’s technical footprint. The shift to Rust makes the binary highly resistant to traditional reverse engineering and significantly accelerates the encryption process.

3. Anatomy of an Attack (The Kill Chain)

A MedusaLocker3 infection is the culmination of a targeted kill chain designed to inflict maximum operational damage.

1. Initial Compromise: Attackers often gain entry by exploiting unpatched perimeter appliances or by brute-forcing exposed Remote Desktop Protocol (RDP) ports (TCP 3389) using purchased credential lists.
2. Lateral Movement & Reconnaissance: Once inside the network, the malware remains dormant while attackers manually explore the environment. They locate active SQL Server instances, domain controllers, and map all connected SAN/NAS devices.
3. Data Exfiltration (The Extortion Setup): Before any files are locked, the attackers identify and siphon sensitive directories to an external server. This guarantees their leverage even if you possess perfect, immutable backups.
4. Execution & Encryption: Upon acquiring elevated privileges, the high-speed Rust payload executes. It purges local shadow copies, terminates locking services, rapidly encrypts the data blocks, appends the .CHUNGACHANGA extension, and drops the RANSOM_NOTE.html notes.

4. The Complete Ransom Note Analysis

During an active incident, the RANSOM_NOTE.html file is a vital piece of forensic evidence. Based on incident response telemetry, below is the reconstructed text typically found in the ransom note left by the MedusaLocker3 operators.

Your personal ID: Key ID: AE61 1C0F F9CB E9E9 D2C1 DF5C DB62 997C E283 C49F C9F6 85B1 BFA3 C305 FFFB E7A5 75E7 520F 929C 10C3 D751 EA05 9C3D BF8A 7B53 F7B1 D66B 0AC8 83CB 6689 6F51 CABF 4923 80B1 FF28 5842 A59F 16EE 43E3 1085 4DFA 3E73 53E0 7820 82B2 F5D2 B2DB 861C EE5D 5275 648E 5DFA 02D8 C9AC 885D 207D B2E9 81C8 D23C A544 1FEF A8E2 BA51 AECE 02B4 28B7 A756 FB9E 2E16 1E0B 8007 253C A37B AAE8 8B3B C33E 27CE CF17 9A82 A0C3 C6AF 9C52 0A52 1997 AF…[Truncted 1618-char Hex String]… YOUR COMPANY NETWORK HAS BEEN PENETRATED ANY ATTEMPT TO RESTORE YOUR FILES WITH THIRD-PARTY SOFTWARE WILL PERMANENTLY CORRUPT IT. DO NOT MODIFY ENCRYPTED FILES. DO NOT RENAME ENCRYPTED FILES. No software available on internet can help you. We are the only ones able to solve your problem. We gathered highly confidential/personal data. These data are currently stored on a private server. This server will be immediately destroyed after your payment. If you decide to not pay, we will release your data to public or re-seller. So you can expect your data to be publicly available in the near future.. We only seek money and our goal is not to damage your reputation or prevent your business from running. You will can send us 2-3 non-important files and we will decrypt it for free to prove we are able to give your files back. Contact us for price and get decryption software. Email: [email protected] [email protected] [email protected] Tor chat address: 723pt5dc2plfexrfvudhdhzvesgesqbcl4yivijjubptnogukxxv3hqd.onion Attention! Instructions and contact information for file recovery are provided in the HTML note “RANSOM_NOTE”. If you try to find a cheap way to decrypt files on forums, you will lose your money and files. YOUR DATA IS ONLY POSSIBLE TO DECRYPTION VIA THE EMAILS IN THE HTML INSTRUCTIONS!!! CONTACT US USING THE CONTACT INFORMATION IN THE NOTE! To contact us, create a new free email account on the site: protonmail.com IF YOU DON’T CONTACT US WITHIN 72 HOURS, PRICE WILL BE HIGHER.

5. Phase 1: Detection & Threat Hunting

Security teams must sweep the environment for the .CHUNGACHANGA extension, the specific HTML ransom notes, and audit the status of the VSS services.

Actionable PowerShell Threat Hunt

Deploy this PowerShell script via your centralized management console (e.g., SCCM or EDR Live Response) to audit servers for MedusaLocker3 indicators:

# ==============================================================================
# Decryptors.org Incident Response Script: MedusaLocker3 (.CHUNGACHANGA) Audit
# Target: Windows Endpoints (Run as Administrator)
# ==============================================================================

Write-Host "Starting MedusaLocker3 Network Audit..." -ForegroundColor Cyan

$infectionFound = $false

# 1. Check for encrypted file extensions
$testPaths = @("C:\Program Files\Microsoft SQL Server", "$env:USERPROFILE\Documents", "D:\Data", "$env:USERPROFILE\Desktop")

foreach ($path in $testPaths) {
    if (Test-Path $path) {
        $files = Get-ChildItem -Path $path -Filter "*.CHUNGACHANGA" -Recurse -ErrorAction SilentlyContinue
        if ($files.Count -gt 0) {
            Write-Warning "[!] CRITICAL: Encrypted .CHUNGACHANGA files detected in $path"
            $infectionFound = $true
        }
    }
}

# 2. Check for the presence of the specific ransom note
$ransomNotes = Get-ChildItem -Path C:\ -Filter "RANSOM_NOTE.html" -Recurse -Depth 4 -ErrorAction SilentlyContinue | Where-Object { Select-String -Path $_.FullName -Pattern "amexmail|CHUNGACHANGA" -Quiet }

if ($ransomNotes) {
    Write-Warning "[!] CRITICAL: MedusaLocker ransom note (RANSOM_NOTE.html) discovered."
    $infectionFound = $true
}

# 3. Check the status of the Volume Shadow Copy (VSS) Service
try {
    $vssEvents = Get-WinEvent -LogName System -MaxEvents 200 -ErrorAction Stop | 
                 Where-Object {$_.Id -eq 7036 -and $_.Message -match "Volume Shadow Copy"}
    
    if ($vssEvents) {
        Write-Warning "[!] Warning: Shadow Copy service modifications detected in recent logs."
        Write-Warning "Threat actors likely executed VSS deletion commands to destroy local backups."
    }
} catch {
    Write-Output "[i] Could not verify VSS service state."
}

if ($infectionFound) {
    Write-Warning ">>> IMMEDIATE SERVER ISOLATION REQUIRED. DO NOT REBOOT. <<<"
} else {
    Write-Output "[i] No immediate signs of MedusaLocker3 infection on this endpoint."
}

7. Phase 3: Cryptographic Triage & Recovery

Once absolute containment is verified and network vulnerabilities have been securely patched, the organization can transition to the recovery phase.

Method 1: The Gold Standard - Restoring from Immutable Backups

The only mathematically guaranteed method for overcoming a MedusaLocker3 attack is a full architectural restoration from verified, completely air-gapped backups.

• The "Clean Room" Rebuild: Because this variant utilizes highly persistent mechanisms, you cannot simply delete the .CHUNGACHANGA files and assume the server is safe. The affected machines must be entirely formatted. Perform a bare-metal OS reinstallation on all impacted hosts.
• Active Directory Cleansing & Credential Rotation: Assume all Active Directory credentials are compromised. Force a global password reset for all users and service accounts. Reset the krbtgt account password twice to invalidate any forged Golden Tickets.
• Sequenced Restoration: Safely migrate your data back from your offline backups into the newly rebuilt, clean environment.

Method 2: Cryptographic Response & Handling Extortion

If your organization lacks recent backups, the situation is extremely severe. MedusaLocker3 utilizes robust modern cryptography. Brute-forcing the encryption key without the attacker's private key is mathematically impossible.

If forensic data carving is not viable and an extortion payment is facilitated as an absolute last resort to recover mission-critical data, you must utilize professional decryption tools operated by DFIR specialists. You must follow a strict, isolated automated decryption workflow:

• Never decrypt on production hardware. The decryption tool provided by the threat actor may be bundled with secondary malware, data stealers, or logic bombs.
• Clone the encrypted drives using professional forensic imaging software.
• Mount the cloned drives on an isolated, air-gapped forensic workstation to perform the decryption.

8. Phase 4: Post-Incident Hardening & Server Resilience

Surviving a MedusaLocker3 attack is a catastrophic operational event. The response to this infection must serve as a mandate for a comprehensive enterprise security overhaul.

• Eradicate Public RDP Exposure: Remote Desktop Protocol (RDP) must never face the public internet. This is the primary entry point for MedusaLocker affiliates. Access to the environment must require a VPN protected by strict multi-factor authentication (MFA).
• Implement Immutable Storage Vaults: You must immediately deploy a modern Veeam 3-2-1-1 backup structure incorporating immutable repositories (such as Linux Hardened Repositories or AWS S3 with Object Lock). Immutable storage guarantees that once backup data is written, it cannot be modified, encrypted, or deleted—even if an attacker explicitly disables the VSS service.
• Deploy Endpoint Detection and Response (EDR): Deploy behavior-based EDR/XDR platforms configured to automatically isolate network adapters on servers that attempt mass file modifications or exhibit lateral movement behaviors.

The MedusaLocker3 (.CHUNGACHANGA) ransomware represents a highly destructive, Rust-based threat focused explicitly on critical data encryption and double-extortion. Navigating this crisis requires a cool head, adherence to strict incident response frameworks, and specialized forensic triage. Should this playbook highlight gaps in your current defensive posture, treat it as a mandate to immediately overhaul your enterprise IT architecture.