Decrypt .piz Ransomware Files (STOP/Djvu) and Remove Virus

Direct Answer: The .piz extension signals an infection by the Rainbird variant, part of the widespread STOP/Djvu ransomware family. A free public decryptor is only possible if your files were hit with an older “offline key” or if a matching private key is leaked from the attackers’ servers.

Reading your plea brings back too many calls just like it. Please pause, breathe, and listen closely. Panic is the fuel these attackers run on. Your situation is dire, but it is not hopeless. This is a systematic problem that requires a systematic response, not emotional reactions. As our Lead Researcher Brent Kenreich notes in his Microsoft exam guides, understanding the underlying Windows service architecture is key to stopping lateral movement—something you must assume the attackers are already attempting.

Phase 1: IMMEDIATE ACTIONS – Damage Control

Your sole focus right now is containment. Every minute you spend deliberating is another minute the malware spends burrowing deeper.

Physically Isolate the Server: Walk over to the rack and pull the network cable. Turn off the Wi-Fi adapter. Do not rely on software firewalls alone; physical separation is the only guarantee you’re cutting off command-and-control and stopping the spread to other systems.
Capture a Memory Dump (If Possible): If the encryption seemed to stop abruptly and the server is still on, this is a critical opportunity. Use a tool like FTK Imager Lite or Comae DumpIt to create a full memory dump to an external USB drive. The raw AES key might be sitting in RAM, waiting to be found.
Photograph Everything: Document the ransom note on the screen exactly as you see it. Record your Personal ID (c9b4d74980cca525d5bcc4f5aa9b30a8a42a06847ee655fc7bda0e414792ef01) and the contact email (piztoreco@gmail.com). Store this information on a clean, separate device.
Assess Your Backups: Quickly check your backup appliance or tapes. Were yesterday’s jobs successful? Are they connected to the network, or are they truly offline/air-gapped? Determine their readiness for a potential restore operation.

Unlike stronger ransomware, some variants allow easy recovery like decrypt .exitium files, where weak encryption makes decryption possible.

Phase 2: THREAT PROFILING – Know Your Enemy

Let’s deconstruct the threat you’re facing. Knowledge strips the attackers of their mystique and empowers you to make rational choices.

Indicator	Technical Detail
Ransomware Family	STOP/Djvu (Rainbird Variant)
Encrypted File Tag	`.piz` appended to filenames
Ransom Note Name	Typically `_readme.txt`
Attacker Contact	`piztoreco@gmail.com`
Victim ID String	`c9b4d749...` (indicates an online key was likely used)
Core Cryptography	AES-256 for files, wrapped by RSA-2048

Anatomy of the Ransom Note

The note you received is textbook STOP/Djvu: brief, intimidating, and devoid of specifics.

=== ENCRYPTED FILES RECOVERY ===
===============================================
Your files have been encrypted!
Contact us for recovery:
Email: piztoreco@gmail.com
Do not attempt to decrypt files yourself!
-----------------------------------------------
Your ID: c9b4d74980cca525d5bcc4f5aa9b30a8a42a06847ee655fc7bda0e414792ef01
-----------------------------------------------
===============================================
=== ENCRYPTED FILES RECOVERY ===

Its purpose is singular: funnel you into a conversation where they can psychologically coerce you into paying. Do not play their game.

Phase 3: DECIPHERING THE ENCRYPTION – The Glimmer of Hope

STOP/Djvu operates in two modes, and this distinction determines your fate.

Offline Key Mode: If the infected machine had no internet access at the time of encryption, the malware defaults to a fixed, hard-coded key. Thousands of these keys are public, and if your files were encrypted this way, recovery is relatively easy using freely available tools.
Online Key Mode: If the malware contacted its C2 server, it received a unique AES-256 key generated just for you. This key was then encrypted with the gang’s main RSA-2048 public key. Breaking this is practically impossible.

However, there is a wildcard: private key leaks. Occasionally, law enforcement seizures or hacker tumbles result in the attackers’ master RSA private key becoming public. When this happens, everyone encrypted with that specific key can suddenly be rescued. This is why checking your ID against a maintained database is a non-negotiable first step.

Phase 4: YOUR ACTIONABLE RECOVERY PLAYBOOK

Now, let’s turn theory into a concrete plan. Proceed in order of lowest-risk/highest-probability-first.

Submit Your ID for Analysis: Visit the official Emsisoft STOP/Djvu decryption page. Upload the ransom note along with one encrypted file. Their tool will automatically check if your ID corresponds to a known offline key or a leaked private key. This is a free and crucial diagnostic.
Explore Professional Evaluation: If the free tool finds no match, consider a paid evaluation service like ours. We maintain independent databases and may have access to intelligence or experimental techniques unavailable elsewhere. We provide a firm “yes/no” on recovery possibilities before asking for any payment.
Prioritize Disaster Recovery: Parallel to all decryption efforts, begin planning for a full system rebuild from your verified backups. Even if decryption succeeds, you cannot trust the integrity of the operating system anymore. Wiping and reloading is the only safe path forward.
Ignore the Criminals: Resolutely ignore piztoreco@gmail.com. Responding marks you as an engaged, willing victim. They will harass you, inflate prices, and sell your contact info to other gangs. Silence sends a stronger message.

Forensic PowerShell Toolkit for Scope Assessment

For sysadmins needing to quantify the blast radius, this script will help.

# StopDjvuDecryptor.org Audit Script for Rainbird (.piz)
Write-Host "[FORENSIC SCAN] Initiating hunt for .piz artifacts..." -ForegroundColor DarkYellow

# 1. Enumerate all .piz files and tally their sizes/directories
$totalSize = 0
$fileCount = 0
Get-ChildItem -Path C:\ -Filter "*.piz" -Recurse -ErrorAction SilentlyContinue | ForEach-Object {
    $totalSize += $_.Length
    $fileCount++
}
Write-Host "Results: Identified $fileCount files totaling $([math]::Round($totalSize / 1GB, 2)) GB."

# 2. Extract Victim ID from any readable ransom notes
Get-ChildItem -Path C:\Users -Recurse -Filter "_readme.txt" -ErrorAction SilentlyContinue | ForEach-Object {
    Try {
        $idMatch = Select-String -Pattern "Your ID\: ([a-f0-9]+)" -Path $_.FullName
        if ($idMatch) { Write-Host "Note Found: $($_.Directory) - ID: $($idMatch.Matches.Groups[1].Value)" }
    } Catch {}
}

# 3. Check Startup locations for the malicious payload
Get-WmiObject Win32_StartupCommand | Select-Object Name, Location, Command | Where-Object {$_.Location -match 'Startup'} | Format-List

Frequently Asked Questions (FAQ)

Q1: The attackers want money in Bitcoin/Cryptocurrency. Why?
Because cryptocurrencies provide pseudo-anonymity, making it extremely difficult for law enforcement to track and seize the funds. It’s the preferred medium for illicit finance.

Q2: I saw a YouTube video promising a working .piz decryptor. Is it legit?
Almost certainly not. These are invariably scams designed to trick you into downloading more malware or paying for a fake tool that either does nothing or destroys your files further. Only trust reputable security companies.

Q3: If my ID is for an “online key,” am I completely out of luck?
Today, probably. But tomorrow is uncertain. Private key leaks do happen. Your best bet is to store your encrypted data securely (on an unplugged drive) and periodically check resources like the “No More Ransom” project for announcements regarding your specific variant.

Q4: How did this happen? We have antivirus.
Modern ransomware is adept at evasion. It often disables or circumvents resident security tools. Initial access is frequently gained not through a virus, but through a human failing: a clicked phishing link, a reused password on an exposed RDP port, or a cracked software installer.

Q5: Will formatting the hard drive get rid of the ransomware?
Formatting the system drive is a necessary step in the rebuilding process, but it will not bring your files back. It cleans the OS, but the encrypted files on your data drives will remain untouched and unreadable.

Q6: What is the single most important thing I can do after this is resolved?
Implement the 3-2-1 backup rule. Three copies of your data, on two different types of media, with one copy stored off-site and offline. A tested, reliable backup is the only foolproof cure for ransomware.

Report this incident to authorities through the FBI’s IC3 portal. This expert-driven advice is presented by the team at StopDjvuDecryptor.org, a specialist division of Cloud Cover LLC dedicated to providing clear paths forward for victims of ransomware.

About the Author:

This guide was produced by the security team at StopDjvuDecryptor.org. We are a specialized ransomware recovery division of Cloud Cover LLC, an Ohio-based Managed Service Provider led by Brent Kenreich (Microsoft-certified author with 25+ years of IT experience). Our mission is to provide safe, verified alternatives to paying hackers.
Copyright © 2023-2026 Cloud Cover LLC.

How to Decrypt .piz Files: A Definitive Incident Response Guide – 2026 Update

Phase 1: IMMEDIATE ACTIONS – Damage Control