1. Executive Summary: The Montage/MedusaLocker Threat

The ransomware landscape is no longer populated by lone-wolf hackers deploying untargeted lock-and-extort campaigns. Today, enterprise IT environments face highly orchestrated, multi-layered cyber-espionage operations run like corporate entities. At the forefront of this evolution is the MedusaLocker syndicate, a highly lucrative Ransomware-as-a-Service (RaaS) group operating since late 2019. Recently, security analysts have identified a devastating new variant under the MedusaLocker umbrella: Montage.

Functionally identical to earlier variants like “Developer” and “Friends”, the Montage ransomware represents a worst-case scenario for enterprise architecture. Once an affiliate gains a foothold, the malware rapidly crawls local drives, mapped network shares, and connected Storage Area Networks (SANs). It encrypts mission-critical files utilizing a military-grade symmetric and asymmetric encryption algorithm combination. It appends a specific numerical extension to the impacted files—for example, a vital database like financial_records.sql is mercilessly transformed into financial_records.sql.montage9 or .montage40, depending on the specific campaign build.

However, the localized encryption of your files is only the most visible half of the attack. The Montage variant is engineered specifically for a double-extortion model. Threat actors quietly exfiltrate terabytes of sensitive intellectual property, employee records, and confidential client data to private offshore servers before the encryption payload is ever executed. This reality transforms a technical IT outage into a severe, legally reportable data breach. Depending on your jurisdiction, this immediately triggers HIPAA, GDPR, or CCPA compliance nightmare scenarios.

This exhaustive, 2000+ word playbook provides IT administrators, network engineers, and incident responders with a clear, user-friendly, and executable roadmap. We will detail how to stop the bleeding, hunt for persistent mechanisms, decode the attacker’s methodology, and execute a safe, systematic recovery operation based on the NIST Incident Response framework.

2. Threat Intelligence & MITRE ATT&CK Matrix

To dismantle a sophisticated adversary, you must first understand their operational capacity and preferred toolsets. Because the MedusaLocker syndicate utilizes a network of independent “affiliates” (Initial Access Brokers) to carry out attacks, the initial point of entry can vary wildly from victim to victim. However, once inside, their execution, defense evasion, and exfiltration tactics remain remarkably consistent.

3. Anatomy of a Montage Attack (The Kill Chain)

Understanding how Montage operates from the moment it touches your network to the moment the ransom note appears is critical for identifying exactly where your security perimeter failed.

1. Initial Compromise: Montage rarely breaks through modern defenses via brute force alone. It usually relies on human error (an employee opening a malicious invoice attachment) or neglected infrastructure (an outdated Fortinet or Pulse Secure VPN appliance with a known CVE vulnerability). Threat actors will also readily purchase compromised RDP credentials on dark web forums to walk right through the front door.
2. Lateral Movement & Privilege Escalation: Once inside, the malware doesn’t encrypt immediately. The attackers use tools like Cobalt Strike, Mimikatz, or Advanced IP Scanner to move laterally. Their primary goal is to compromise the Active Directory Domain Controller and steal an Enterprise Admin account credential.
3. Data Exfiltration: Using legitimate tools like Rclone or MegaSync, the attackers siphon your most valuable data to their cloud servers. Because these tools are “legitimate,” they often bypass standard firewall outbound rules.
4. Defense Evasion & Encryption: With data secured offsite, the attackers deploy the Montage payload via Group Policy (GPO) or tools like PsExec to all endpoints simultaneously. The malware executes vssadmin.exe Delete Shadows /All /Quiet to destroy local backups, halts database services (SQL, Exchange) to unlock files, and begins the rapid encryption process.

4. The Complete Montage Ransom Note Analysis

During an active incident, the ransom note is a vital piece of forensic evidence. It provides the affiliate ID, the TOR negotiation portal, and the unique RSA public key identifier required by any potential decryption utilities. Below is the complete, unaltered text of the Montage RANSOM_NOTE.html file.

Your files have been encrypted. Key ID: [Unique Victim Alphanumeric String] Contact us for price and get decryption software. 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] * 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

Once an infection is suspected, detection must scale rapidly. Security teams need to deploy sweeping scans across the entire Active Directory environment to locate the malicious binary and strip away its persistence mechanisms.

Actionable PowerShell Threat Hunt

Montage variants ensure they execute every time an administrator logs in by writing to the Windows Registry. Deploy this PowerShell script via your centralized management tool (e.g., PDQ Deploy, SCCM, or EDR Live Response) to audit your endpoints for MedusaLocker/Montage indicators:

# ==============================================================================
# Decryptors.org Incident Response Script: Montage / MedusaLocker Audit
# Target: Windows Endpoints (Run as Administrator)
# ==============================================================================

Write-Host "Starting Montage/MedusaLocker Audit..." -ForegroundColor Cyan

# 1. Check for suspicious VSS deletion events in the Windows Event Log
# Event ID 7036 often correlates with the Volume Shadow Copy service state changing unexpectedly
try {
    $vssEvents = Get-WinEvent -LogName System -MaxEvents 100 -ErrorAction Stop | 
                 Where-Object {$_.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: vssadmin.exe Delete Shadows /All /Quiet"
    } else {
        Write-Output "[i] No recent VSS manipulation detected in System logs."
    }
} catch {
    Write-Output "[i] Could not parse Event Logs or no logs found."
}

# 2. Check for the known malicious executable drop locations
# MedusaLocker variants often drop in AppData or ProgramData
$suspiciousPaths = @(
    "$env:APPDATA\svhost.exe",
    "$env:APPDATA\montage.exe",
    "$env:ProgramData\winlogon.exe"
)

foreach ($path in $suspiciousPaths) {
    if (Test-Path $path) {
        Write-Warning "[!] CRITICAL: Malicious payload found at $path"
        Write-Warning "Immediate endpoint isolation required."
    }
}

# 3. Check for encrypted file extensions in critical directories
$testPath = "$env:USERPROFILE\Documents"
$encryptedFiles = Get-ChildItem -Path $testPath -Filter "*.montage*" -Recurse -ErrorAction SilentlyContinue

if ($encryptedFiles.Count -gt 0) {
    Write-Warning "[!] CRITICAL: Encrypted .montage files detected in User Documents."
} else {
    Write-Output "[i] No .montage extensions found in primary user directory."
}

7. Phase 3: Tiered Recovery & Decryption Strategies

Once containment is verified and the initial access vector (such as a compromised firewall appliance or a weak RDP password) has been securely patched, the organization can move to the recovery phase. This must be executed methodically to prevent reinfection.

Method 1: The Gold Standard – Restoring from Immutable Backups

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

• The “Clean Room” Rebuild: You cannot simply run antivirus software (like Malwarebytes or Combo Cleaner) and assume the server is safe for production data. Threat actors leave persistent, hidden backdoors (like Cobalt Strike beacons or disguised AnyDesk instances). Affected hard drives must be 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. Crucially, reset the krbtgt account password twice to invalidate any Golden Tickets the attackers may have forged. Audit AD for any recently created, unauthorized administrator accounts.
• Sequenced Restoration: Follow your cross-platform recovery map meticulously. Restore Domain Controllers first in an isolated VLAN to establish DNS and authentication. Once stable, restore database servers, and finally, user file shares.

Method 2: Decryption Utilities & Cryptographic Response

If your organization lacks immutable backups, the situation is dire. The Montage variant utilizes robust cryptography, meaning simple brute-forcing of the key is mathematically impossible. However, specialized incident response firms sometimes uncover flaws in how specific threat actors implement their key generation.

A stern warning regarding “middlemen”: The ransom note correctly states, “Beware of middlemen, they come to us with your files, decrypt them and show themselves as if they decrypted them, take your money and disappear.” Many online “data recovery” firms simply negotiate with the hackers on your behalf and charge you a massive markup. You must work with verified cryptographic experts.

If a legitimate decryptor becomes available, or if a ransom is paid and the threat actor provides a decryption tool, you must follow a strict, isolated automated decryption workflow:

1. Never decrypt on production hardware. The tool provided by the threat actor may contain secondary malware, data stealers, or logic bombs.
2. Clone the encrypted drives using professional forensic imaging tools.
3. Mount the cloned drives on an isolated, air-gapped workstation.
4. Run the decryption utility against the clone, not the original.
5. Verify the file integrity of the decrypted data.
6. Scan the decrypted files with multiple EDR engines before moving them back to the production environment.

8. Phase 4: Future Hardening & Resilience

Experiencing a Montage attack is a catastrophic operational burden. The response to the infection must serve as a catalyst for a comprehensive enterprise security overhaul. The ultimate goal is to move your IT environment from a reactive, vulnerable posture to a proactive, resilient architecture.

• Implement Immutable Storage Vaults: A modern Veeam 3-2-1 backup structure is now mandatory, not optional. You must incorporate immutable repositories (such as Linux Hardened Repositories, AWS S3 with Object Lock, or Wasabi immutable buckets). Immutable storage guarantees that once data is written, it cannot be modified, encrypted, or deleted for a specified period—even by a threat actor who has successfully stolen Domain Admin credentials and executed the vssadmin.exe command.
• Eradicate Public RDP Exposure: Remote Desktop Protocol should never face the public internet under any circumstances. Access to the environment must require a VPN protected by strict multi-factor authentication (MFA), followed by a connection through a hardened jump-box or PAM (Privileged Access Management) solution.
• Deploy Endpoint Detection and Response (EDR): Legacy signature-based antivirus is blind to modern, fileless ransomware techniques. Deploy behavior-based EDR/XDR platforms (like CrowdStrike, SentinelOne, or Microsoft Defender for Endpoint) configured to automatically isolate network adapters on hosts that attempt mass file modifications or exhibit lateral movement behaviors.
• Enforce the Principle of Least Privilege (PoLP): Regular users should not have local administrator rights on their workstations. Furthermore, service accounts should be heavily restricted. If an attacker compromises a standard user account via a phishing email, they should not be able to traverse the network freely to reach critical servers.

The Montage variant of MedusaLocker is a highly sophisticated, financially motivated threat. Navigating this crisis requires a cool head, adherence to strict incident response frameworks, and a methodical approach to containment. Should this playbook highlight gaps in your current defensive posture, treat it as a mandate to immediately overhaul your enterprise IT infrastructure.