Parasite file virus: what it is and how to remove it
It is a computer virus that encrypts personal victim data with military-grade RSA-2048 and RC4 encoding algorithms. It demands payment in cryptocurrency Bitcoins (through @READ_ME_FILE_ENCRYPTED@.html ransom note) for said file decryption.
Facts checked October 7, 2026. Removal steps tested on Windows 11 (26H2) and checked against Microsoft's and the browser makers' current documentation. Sections marked as our earlier report are the original text: they describe the threat as it was then and have not been reviewed since. The 2026 status, the removal steps and the questions are current.
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Parasite file virus: summary
| name | Parasite file virus |
|---|---|
| Type | File-locking virus, cryptovirus |
| Encryption algorithm | RSA-2048 and RC4 |
| Appended file extension | .parasite extension is appended to all original filenames |
| Ransom note | @READ_ME_FILE_ENCRYPTED@.html; the text is quoted in full below |
| Preferred payment method | Cryptocurrency Bitcoins |
| Removal | Scan the PC with security software to find and remove the malware and anything installed with it. Fortect scans Windows for malware and repairs the system files and settings it damaged. Remove it nowTo use the full-featured product, you have to purchase a license for Fortect. The scan is free. |
Show 15 more facts
| Malware removal | All computer infections must be eliminated by using trustworthy anti-malware software |
|---|---|
| Detection names | No Microsoft detection name is known |
| Contact | parasiteciph@tutanota.com, parasiteCIPH@tutanota.com |
| Encrypted file extension | .parasite |
| Decryptor | No free decryptor is known for this variant; check No More Ransom (nomoreransom.org) for updates |
| Distribution | Not recorded in the old report |
| Damage | Not recorded in the old report |
| Name | Parasite file virus |
| Symptoms | Files renamed with a new extension, a Windows Security "Threats found" notification and a ransom note left in folders |
| Evidence | 5 write-ups by security sites; no sample analysed yet |
| Encrypted files | .parasite |
| Free decryptor | No free decryptor is known (checked 7 October 2026) |
| First seen | 11 April 2021 |
| Microsoft Defender name | Ransom:MSIL/FileCoder!MTB |
| Facts checked | 7 October 2026 |
Parasite file virus detection names
If Windows Security shows Ransom:MSIL/FileCoder!MTB, it has found Parasite file virus or a file that belongs to it.
Write the name down before you click Remove: it is the most useful search term later, and you will need it if you report the incident.
A family name in the label is more informative than a heuristic one. Our page on why one threat has many antivirus names lists the common formats and what each part means.
- File extension:
.parasite - Note file:
the ransom note
From our report of Apr 2021 · not reviewed since
Learn to identify spam emails to avoid ransomware
We've all received spam emails in our lives, but little did you know that ransomware developers love to spread their creations through them.
The infections are usually hidden either as an email attachment or in a hyperlink. These emails might look like legitimate letters from your beloved store, bank, shipping company, etc.
But as soon as any of the aforementioned options are clicked, your device's files might be locked within minutes. Our team compiled a set of signs that would help everyday computer users to identify these threats. Please don't open any email attachments or hyperlinks if an email consists of any of these indications:
- You're addressed in a general manner, instead of your full name.
- You are urged to visit a site through a given hyperlink immediately.
- The email is written in poor grammar.
- The sender's domain doesn't exactly match the domain of the company.
- You're pushed to download the attachment because it contains some critical updates/data.
- Email senders ask to provide them sensitive information.
From our report of Apr 2021 · not reviewed since
More from our earlier report on Parasite file virus
- Victims of ransomware should use powerful system repair tools like the app to fix any system issues the cyber infection might have caused
How Parasite file virus behaves
From our report of Apr 2021 · not reviewed since
Parasite ransomware – a file-locking virus that exploits its victims for monetary gain
It is a computer virus that encrypts personal victim data with military-grade RSA-2048 and RC4 encoding algorithms.
It demands payment in cryptocurrency Bitcoins (through @READ_ME_FILE_ENCRYPTED@.html ransom note) for said file decryption.
The virus also renames all files by appending the .parasite extension - this is where malware gets its name from. Data is inaccessible until a required decryption tool is used. Unfortunately, it's tough to do without the help of the cybercriminals who would prefer to be contacted via this email - parasiteciph@tutanota.com.
If any of your devices were affected by this file-locking malware, then you chose the right place to learn more about it and find out how to remove it. This article contains information about the Parasite virus, including distribution techniques used to deliver it and its removal options.
All ransomware generates some sort of ransom notes when the encryption of data is completed. With some, it might be text files (Wbxd virus, Cring virus), while others (Dis virus), in addition to text files, can create pop-up windows too. This ransomware, however, creates an .HTML file ransom note.
Within it, cybercriminals explain what happened to the victim files and what they should do to restore them. The main goal of these notes is to scare or convince victims into meeting the demands of their assailants. Developers of Parasite virus want to be contacted via a given email so they could provide ransom details because apart from the preferred payment method, the ransom amount isn't specified.
The whole message from the cyber thieves is long and can be read here:
Although it might seem that meeting the criminals' demands is the easiest way out of this sticky situation, it's the worse thing any ransomware victims can do. And here's why:
The only way to stop ransomware creators from infecting the computers of innocent people is by not paying them. If victims stopped succumbing to their assailants, new file-locking parasites wouldn't be created, and hopefully, the attacks would stop.
That's why our cybersecurity team highly recommends victims remove ransomware from their infected devices. Best results are achieved when doing that with a professional anti-malware tool such as or . Scan your entire system and let the software do the rest.
Malware usually makes changes to system files and system settings. That could lead to various system issues, such as freezing, crashing, etc. So once Parasite ransomware removal is finished, experts recommend performing a system repair with powerful system tune-up tools like or similar.
- Received money motivates the criminals to increase their attacks.
- It finances their development of more sophisticated malware.
- It provides funds for research of more efficient ways of payload file delivery.
The Parasite file virus ransom note
Your ID is: -
All your files are encrypted !
Hello! All your files have been encrypted using RSA-2048 and RC4 encryption algorithm. You can learn about cryptography and encryption algorithm here RSA-2048 (Wikipedia) and RC4 (Wikipedia)
That's why your files are no longer readable.
It means that the contents of your files have been changed and you can't use them as before. It is like loosing your files forever.
How can I recover my files ?
If you understand the importance of the situation, Then you can ask for the decryption of your files.
To decrypt your files, you need to purchase your private key.
The price can change every day so don't waste your time ! You can ask for the payement (in bitcoin) by email: parasiteCIPH@tutanota.com
Please specify your ID in the subject of your message.
Once you paid, you will receive your key and the decryption tool.
How can I buy bitcoins ?
To buy bitcoins, you can follow these links:
hxxps://localbitcoins.com
hxxps://bitcoin.org
hxxps://www.bitcoin.com
hxxps://www.coinbase.com
You can learn more about the bitcoins here
Should I trust you ?
Yes, you can trust us.
Our mission is to decrypt your files. You pay, we help.
Remember that if you don't want to pay you will not be able to get you files back.
Attention !
Only communication through our email can guarantee file recover for you. We are not responsible for the actions of third parties who promise to help you most often they are scammers.
Please, do not try to rename encrypted files.
If you want to make sure that it is impossible to recover files using third-party software, do this not on all files, otherwise you may lose all data.
Our goal is to return your data, but if you don't contact us, we will not succeed
How to remove Parasite file virus
Tools you'll need
All of these are free except where noted. Download them on a clean device if the infected PC is offline.
- A USB stick: to keep the ransom note, two or three encrypted files and screenshots off the infected PC.
- Microsoft Defender Offline: built into Windows 11 and Windows 10; scans before Windows starts, so running malware cannot hide.
- Microsoft Safety Scanner: a second, portable scanner with current signatures; each download works for 10 days.
- ID Ransomware: identifies the family from the note and one encrypted file and says whether a decryptor exists.
- No More Ransom: the free decryptors from police and security companies; check it again every few months.
- Fortect (optional): scans Windows for malware and repairs the system files and settings it damaged. The free scan is in the box above.
How to remove Parasite file virus and get your files back
Work in this order.
Disconnecting comes first, removal comes before any restore, and nothing here asks you to contact the attackers.
Step 1: Disconnect the PC and unplug backup drives
Parasite file virus encrypts everything it can reach, including drives and shares you connect later. Cut the network first: cable out, or Wi-Fi off from the taskbar.
Then unplug every USB stick and backup disk and pause cloud sync, so the encrypted versions do not replace your online copies. Do not reconnect any of them until the ransomware is removed from the Windows 11 or Windows 10 PC.
Windows 11: turn off Wi-Fi to take the PC offline. Full procedure with screenshots: Ransomware: first steps, finding a decryptor and recovering files
Step 2: Save the ransom note and confirm the family
Copy
the ransom noteand one or two files ending in.parasiteto a USB stick, and leave the originals where they are.From another device, upload the note and a sample file to ID Ransomware or No More Ransom's Crypto Sheriff, which name the family from the note, the extension and the file structure.
Write down the contact address and your personal ID from the note, because a decryptor or the police may ask for them.
Warning: Never contact the attackers from the infected Windows 11 or Windows 10 PC.
Windows 11: the ransom note and encrypted files to copy for identification. Full procedure with screenshots: Ransomware: first steps, finding a decryptor and recovering files
Step 3: Check for a free decryptor
For Parasite file virus, no free decryptor is known (checked 7 October 2026). Search the family name in the No More Ransom decryption tools list and in the free decryptors of Emsisoft, Avast and Kaspersky, because new tools appear years after an attack.
Important: Keep the encrypted files even if nothing works today, and do not pay before every free option is ruled out: payment does not guarantee a working key.
Decryptors run on Windows 11 and Windows 10, but only after the ransomware itself is removed.
Full procedure with screenshots: Ransomware: first steps, finding a decryptor and recovering files
Step 4: Remove the ransomware before you restore or decrypt
Restoring or decrypting files while Parasite file virus still runs lets it encrypt them again. Run a Full scan in Windows Security > Virus & threat protection > Scan options, then the Microsoft Defender Antivirus (offline scan).
If the ransomware blocks Windows Security, start Safe Mode with Networking and scan from there. Some families install a password stealer as well, so let both scans finish on Windows 11 or Windows 10.
Windows 11: Windows Security > Virus & threat protection > Scan options. Full procedure with screenshots: Run a Microsoft Defender Offline scan
Step 5: Look for shadow copies of the files
Open Command Prompt as administrator and run
vssadmin list shadows. If it lists copies dated before the attack, right-click a folder with encrypted files in File Explorer, choose Properties > Previous Versions, and open or restore a version from before that date.ShadowExplorer, a free tool, shows the same copies when the tab is empty or hidden. Most current families delete shadow copies, so an empty list is normal, but the check takes two minutes on Windows 11 or Windows 10.
Windows 11: vssadmin list shadows shows whether shadow copies exist. Full procedure with screenshots: Ransomware: first steps, finding a decryptor and recovering files
Step 6: Restore the files from a backup or recover deleted originals
Restore from an external backup, File History or OneDrive's version history, choosing a date before the attack. Connect the backup drive only after the scans are clean, or the ransomware encrypts it too.
If there is no backup, file recovery software can sometimes find the deleted originals, because some ransomware writes an encrypted copy and deletes the original file.
Stop writing to the drive and try recovery on Windows 11 or Windows 10 before new files overwrite the space.
Full procedure with screenshots: Recover deleted files (Recycle Bin, backups, OneDrive) On uGetFix
Instructions for each browser and system
The detailed steps for every browser and system this guide covers. Open the one you use.
Manual removal using Safe Mode
Important! →
Manual removal guide might be too complicated for regular computer users. It requires advanced IT knowledge to be performed correctly (if vital system files are removed or damaged, it might result in full Windows compromise), and it also might take hours to complete. Therefore, we highly advise using the automatic method provided above instead.
Step 1. Access Safe Mode with Networking
Manual malware removal should be best performed in the Safe Mode environment.
Windows 7 / Vista / XP
- Click Start > Shutdown > Restart > OK.
- When your computer becomes active, start pressing F8 button (if that does not work, try F2, F12, Del, etc. - it all depends on your motherboard model) multiple times until you see the Advanced Boot Options window.
- Select Safe Mode with Networking from the list.
Windows 10 / Windows 8
- Right-click on Start button and select Settings.
- Scroll down to pick Update & Security.
- On the left side of the window, pick Recovery.
- Now scroll down to find Advanced Startup section.
- Click Restart now.
- Select Troubleshoot.
- Go to Advanced options.
- Select Startup Settings.
- Press Restart.
- Now press 5 or click 5) Enable Safe Mode with Networking.
Step 2. Shut down suspicious processes
Windows Task Manager is a useful tool that shows all the processes running in the background. If malware is running a process, you need to shut it down:
- Press Ctrl + Shift + Esc on your keyboard to open Windows Task Manager.
- Click on More details.
- Scroll down to Background processes section, and look for anything suspicious.
- Right-click and select Open file location.
- Go back to the process, right-click and pick End Task.
- Delete the contents of the malicious folder.
Step 3. Check program Startup
- Press Ctrl + Shift + Esc on your keyboard to open Windows Task Manager.
- Go to Startup tab.
- Right-click on the suspicious program and pick Disable.
Step 4. Delete virus files
Malware-related files can be found in various places within your computer. Here are instructions that could help you find them:
- Type in Disk Cleanup in Windows search and press Enter.
- Select the drive you want to clean (C: is your main drive by default and is likely to be the one that has malicious files in).
- Scroll through the Files to delete list and select the following:
Temporary Internet Files
Downloads
Recycle Bin
Temporary files - Pick Clean up system files.
- You can also look for other malicious files hidden in the following folders (type these entries in Windows Search and press Enter):
%AppData%
%LocalAppData%
%ProgramData%
%WinDir%
After you are finished, reboot the PC in normal mode.
From our report of Apr 2021 · not reviewed since
Guidelines for Ransomware removal and a quick but important system repair
If your device was infected with Parasite virus, that means your anti-virus software failed you.
Maybe its virus database was out of date or it's just incapable of catching hazardous malware.
According to VirusTotal , 49 out of 71 anti-virus tools caught the infection and prevented it from encrypting personal data. Here's a few examples of its detection names:
The only right thing do to after you get your computers contaminated is to get rid of the infection. People shouldn't ever consider meeting the demands of the criminals. So remove ransomware with anti-malware software to ensure it's completely eliminated.
Afterward, run a system repair with or similar powerful system tune-up tools. This will get your device back on it's feet and prevent it from exhibiting any abnormal behavior such as the blue screen of death, severe lag, crashing, freezing, and so on.
[GI=method-1]If prevented otherwise, virus elimination can be done in Safe Mode with Networking
[GI=method-2]Using System Restore for threat deletion
This app could be able to recover .parasite extension files.
Data could also be recovered with Windows Previous Version feature
This Windows OS feature could allow users to restore .parasite extension files individually, i.e., one at a time.
Data recovery with Shadow Explorer
If Shadow Volume Copies are still intact, Shadow Explorer could help to restore lost data.
No decryption tool is currently available
- Ransom:MSIL/FileCoder!MTB
- ML.Attribute.HighConfidence
- Win32:RATX-gen
- HEUR:Trojan.Win32.Generic
- GenericRXIQ-YQ!1BE0E2B3B59A
Report it and recover your files
Report it
Report the attack even if you do not expect the files back: insurers and banks ask for the report number, and police use the contacts in the note to link cases.
- United States
- FBI IC3 · FTC ReportFraud
- United Kingdom
- Report Fraud (formerly Action Fraud) · NCSC
- Australia
- ReportCyber (ASD)
- EU countries
- Europol: national reporting sites
Give the victim ID, the note and the date the files were encrypted. A business that holds personal data may also have to notify its data protection authority, in the EU within 72 hours.
Backups: the 3-2-1 rule
Keep three copies of files that matter, on two kinds of storage, with one copy offline or off-site.
A disk that stays plugged in is reached by malware like Parasite file virus together with the PC; one you connect only for the backup is not.
On Windows 11, File History keeps versions on an external drive, and OneDrive keeps earlier versions of synced files. Before restoring anything, make sure the PC no longer shows files that end in .parasite and no longer open.
Setting it up step by step: 3-2-1 backups on Windows 11 and 10.
Protect your privacy - employ a VPN
There are several ways how to make your online time more private - you can access an incognito tab.
However, there is no secret that even in this mode, you are tracked for advertising purposes. There is a way to add an extra layer of protection and create a completely anonymous web browsing practice with the help of VPN. This software reroutes traffic through different servers, thus leaving your IP address and geolocation in disguise.
Besides, it is based on a strict no-log policy, meaning that no data will be recorded, leaked, and available for both first and third parties. The combination of a secure web browser and VPN will let you browse the Internet without a feeling of being spied or targeted by criminals.
No backups? No problem. Use a data recovery tool
If you wonder how data loss can occur, you should not look any further for answers - human errors, malware attacks, hardware failures, power cuts, natural disasters, or even simple negligence.
In some cases, lost files are extremely important, and many straight out panic when such an unfortunate course of events happen. Due to this, you should always ensure that you prepare proper data backups on a regular basis.
If you were caught by surprise and did not have any backups to restore your files from, not everything is lost. is one of the leading file recovery solutions you can find on the market - it is likely to restore even lost emails or data located on an external device.
Questions about Parasite file virus
Can a data-recovery company decrypt my files for a fee?
Only if a decryptor already exists or the company pays the attackers for you. Some "ransomware recovery" services advertise that they can decrypt families with no known flaw; in practice they negotiate with the attackers and add their own fee. Others use the same free tools listed on No More Ransom.
Before you hire anyone, ask in writing how they will recover the files, whether they will contact the attackers and what happens if they fail. A legitimate service answers clearly. If a free decryptor exists for your family, you can run it yourself.
How do I open .parasite files?
You cannot open them by renaming or by choosing another program. The .parasite ending shows that Parasite file virus encrypted the content, and only the matching key can reverse it. Renaming a file back to .docx or .jpg changes nothing except the icon, and it can confuse a future decryptor, so leave the names as they are.
To get the content back, use a backup, an unencrypted copy elsewhere, or a decryptor listed on No More Ransom if one exists for Parasite file virus. Store the encrypted files on an external disk until then.
Is there a free Parasite file virus decryptor?
We last checked on 7 October 2026, and for Parasite file virus no free decryptor is known. We check No More Ransom, which collects free tools from police and security companies, and the decryptor pages of the major antivirus vendors. A working decryptor exists only when the encryption has a flaw or the keys were leaked or seized.
Ignore sites and videos that offer a "Parasite file virus decryptor" for download or for a fee: these are usually scams or malware. Real decryptors are free and come from known security companies or law enforcement. Keep the encrypted files in case a tool appears later.
Should I pay the ransom?
We advise against it, and so do the FBI, Europol and national cyber agencies. Payment does not guarantee a working tool: some attackers never reply, some tools damage files, and some variants have no decryptor at all. Paying also funds further attacks and can make you a target again.
Before considering payment, try every recovery option in this guide and report the attack. Companies must involve their legal adviser and insurer, because payments to sanctioned groups can be illegal. If files are truly irreplaceable, store the encrypted copies and wait; decryptors sometimes appear later.
How did Parasite file virus get on my computer?
The way Parasite file virus spreads has not been documented yet, so look at your own recent activity. On home PCs, ransomware most often comes with cracked programs, game cheats, key generators and fake updates, or with an e-mail attachment that was opened. On business networks, attackers usually log in through Remote Desktop with a stolen or guessed password.
Think back to what was downloaded or installed in the days before files that end in .parasite and no longer open, and check the Downloads folder and Installed apps sorted by date. Keep anything suspicious for your report, but do not run it again.
Did Parasite file virus steal my files or passwords?
We do not know yet. Nothing published so far shows data theft by Parasite file virus, but the only confirmed sign is files that end in .parasite and no longer open, which says nothing about what happened before. Many current ransomware attacks copy files or run a password stealer first, so it is wise to act as if they did.
From a clean device, change the passwords that were saved in the browsers on this PC, starting with e-mail and banking, sign out of all sessions and turn on two-step verification. Watch bank statements and account activity for the next few weeks.
Is Parasite file virus the same as other ransomware with a similar name?
Not necessarily. Ransomware names come from the file extension, the note or a word in the code, so unrelated families often end up with similar names, and one family can appear under several names. The difference matters: a decryptor or advice for one family does not fit another and can damage files.
Compare the ending added to your files and the exact name of the note with the summary table at the top of this guide, then upload the note and one encrypted file to ID Ransomware from a clean device. If the result names another family, follow the guide for that family instead.
Can I just remove .parasite from the file names?
You can try it on a copy, but for real ransomware it will not help. The .parasite extension is only a label; the file content has been scrambled with a key the attackers hold.
If a renamed copy opens normally, the malware only renamed files, which happens with some fake ransomware, and you can rename the rest back. If it does not open, leave the files as they are. Renaming encrypted files can confuse a decryptor later, so always work on copies.
What does the name Ransom:MSIL/FileCoder!MTB tell me?
Microsoft builds names in a fixed order:
- category
- then platform
- then family
- sometimes followed by a variant letter
- a suffix
The category is the most useful part for you. Trojan, Backdoor and PWS mean real malware that can download more, give remote access or steal passwords. PUA means unwanted software.
Ransom means ransomware. Suffixes such as !ml or !MTB mean the detection came from machine learning or behaviour analysis. Search for the family part of Ransom:MSIL/FileCoder!MTB together with the word Microsoft to find its entry in Microsoft's security encyclopedia.
Will Fortect remove Parasite file virus?
Fortect scans Windows for malware and unwanted programs and repairs the system files and settings they change, and its free scan shows what it finds on your PC before you decide anything.
For Parasite file virus, follow the plan above as well: the browser steps take back permissions and settings that no scanner treats as a threat, and uninstalling the program that brought it removes the source.
Run Microsoft Defender's full scan and, if anything was found, its offline scan as a second opinion. If the symptoms are gone after the plan and both scans are clean, there is nothing more to do.
Sources
- Cryptobook: The RSA Cryptosystem - Concepts (read October 7, 2026)
- Geeksforgeeks: What is RC4 Encryption? (read October 7, 2026)
- Virustotal: VirusTotal (read October 7, 2026)
- CISA: StopRansomware (read October 7, 2026)
- No More Ransom (read October 7, 2026)