Iisa virus: what it is and how to remove it
Iisa virus is an extortion-based program from cybercriminals who are focused on money demands. The encryption process is used to create issues with the machine, so once the ransom note appears on the screen, victims get straight to payment and think that data can be restored.
Facts checked October 6, 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.
Automatic
Get a free scan and check if your PC is infected.
Fortect finds malware, unwanted programs and the Windows damage they leave behind, and repairs it in one pass.
Before you restore backups, a full scan can confirm the program that added .iisa is gone.
Do it yourself · free Remove Iisa virus yourself 6 steps, about 18 minutes, no software needed.
Start the steps
Iisa virus: summary
| Distribution | Spam email attachments, software cracks, game cheats, and other files delivered online can contain virus payload |
|---|---|
| Name | Iisa virus |
| Type | Ransomware, file-locker, cryptovirus |
| Family | Djvu/STOP ransomware |
| File extension | .iisa gets added at the end of every original filename |
| Ransom note | _readme.txt |
| 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 13 more facts
| Contact | manager@mailtemp.ch and helprestoremanager@airmail.cc |
|---|---|
| Ransom amount | $490/$980 |
| Detection names | No Microsoft detection name is known |
| Encrypted file extension | .iisa |
| Decryptor | No free decryptor is known for this variant; check No More Ransom (nomoreransom.org) for updates |
| Damage | Not recorded in the old report |
| Symptoms | Files renamed with a new extension and a ransom note left in folders |
| Evidence | 4 write-ups by security sites; no sample analysed yet |
| Encrypted files | .iisa |
| Attacker contacts | manager@mailtemp.ch |
| Free decryptor | No free decryptor is known (checked 6 October 2026) |
| First seen | 19 November 2021 |
| Facts checked | 6 October 2026 |
- File extension:
.iisa - Note file:
_readme.txt - Contact:
manager@mailtemp.ch
From our report of Oct 2026 · not reviewed since
More from our earlier report on Iisa virus
- It is possible that many issues are created due to the virus damage on the machine, so repair the affected files and settings yourself
How to remove Iisa 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 Iisa 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
Unplug the network cable or turn off Wi-Fi, and disconnect USB drives, external disks and network shares, so Iisa virus cannot reach more files. Pause OneDrive, Google Drive or Dropbox sync, because synced folders upload the encrypted copies over the good ones.
Leave the PC on but offline while you read the next steps, since a restart can let the ransomware run again. This applies to Windows 11 and Windows 10 alike.
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
Your files now end in
.iisaand the instructions are in_readme.txt. Save both to a USB stick, a copy of the note and two small encrypted files, before anything else.On another device, check them with ID Ransomware or Crypto Sheriff: the family name decides which decryptor, if any, can help. Keep the note's ID and contact line for your report.
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
Our last check found that for Iisa virus, no free decryptor is known (checked 6 October 2026). Look again yourself in the No More Ransom list and the free decryptor pages of Emsisoft, Avast and Kaspersky, which add new families every year.
A decryptor needs the ransomware gone first, or it encrypts the files again. Keep at least one copy of the encrypted files on an external drive, even if no tool works yet.
Full procedure with screenshots: Ransomware: first steps, finding a decryptor and recovering files
Step 4: Remove the ransomware before you restore or decrypt
Removing Iisa virus does not bring the files back, but it has to come first. Start with Defender's Full scan, then the offline scan from the same Scan options page, which checks the disk before Windows loads.
If the scan cannot start, use Safe Mode with Networking. Delete the ransom notes only after you have saved a copy, because removal tools sometimes leave them behind on Windows 11 and 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
Windows keeps shadow copies for restore points and backups, and some ransomware fails to delete them.
vssadmin list shadowsin an administrator Command Prompt tells you at once whether any exist.If they do, right-click the folder that held your files, open Properties > Previous Versions, select a version from before the attack, and click Open to check it before you Restore or copy the files out. Windows 11 and Windows 10 both have the tab.
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
A backup made before the attack is the surest way back. Connect it only once the PC is clean, then restore from File History, Windows Backup, OneDrive's Restore your OneDrive or your own external copies.
Without a backup, try file recovery: the originals that Iisa virus deleted may still be on the disk until something overwrites them. Install nothing new on the drive you want to recover from on the Windows 11 or Windows 10 PC.
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.
Restore Windows "hosts" file to its original state
Some ransomware might modify Windows hosts file in order to prevent users from accessing certain websites online. For example, Djvu ransomware variants add dozens of entries containing URLs of security-related websites, such as 2-spyware.com. Each of the entries means that users will not be able to access the listed web addresses and will receive an error instead.
Here's an example of "hosts" file entries that were injected by ransomware:
In order to restore your ability to access all websites without restrictions, you should either delete the file (Windows will automatically recreate it) or remove all the malware-created entries. If you have never touched the "hosts" file before, you should simply delete it by marking it and pressing Shift + Del on your keyboard. For that, navigate to the following location:
C:\\Windows\\System32\\drivers\\etc\\
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.
Important steps to take before you begin malware removal
File encryption is one component of a ransomware infection, which may also include credential theft, persistence mechanisms, and lateral movement. However, it is important to understand that malware may perform various changes within a Windows operating system, including persistence, scheduled tasks, registry modifications, and security feature tampering.
IMPORTANT for those without backups! →
If you attempt to use security or recovery software immediately, you might permanently damage your files, and even a working decryptor then would not be able to save them.
Before you proceed with the removal instructions below, you should copy the encrypted files onto a separate medium, such as USB flash drive or SSD, and then disconnect them from your computer. The storage device should remain disconnected after copying to prevent accidental modification or deletion. Encrypted data itself does not contain active malicious code, but only the encrypted files—not executables or scripts—should be transferred.
The instructions below might initially seem overwhelming and complicated, but they are not difficult to understand as long as you follow each step in the appropriate order. This comprehensive free guide will help you to handle the malware removal and data recovery process correctly.
If you have any questions, comments, or are having troubles with following the instructions, please do not hesitate to contact us via the Ask Us section.
IMPORTANT! →
It is vital to eliminate malware infection from the computer fully before starting the data recovery process, otherwise ransomware might re-encrypt retrieved files from backups repeatedly.
Create data backups to avoid file loss in the future
Report the incident to your local authorities
Ransomware is a lucrative, highly illegal business, and authorities are actively targeting ransomware operators. The level of investigation and follow-up depends on the country, the scale of the incident, and whether the attack is linked to known ransomware groups. To increase the likelihood of identifying the culprits, the agencies need information. In many cases, reports are used primarily for intelligence gathering, trend analysis, and victim support rather than immediate identification of attackers.
Therefore, by reporting the crime, you could help stop the cybercriminal activities and catch the threat actors. Reporting does not guarantee investigation or recovery of data, but it contributes to broader efforts to track ransomware campaigns. Make sure you include all the possible details, including how did you notice the attack, when it happened, etc. Relevant details may also include affected systems, ransom demands, cryptocurrency wallet addresses, and any communication with the attackers. Additionally, providing documents such as ransom notes, encrypted files, or malware executables would be beneficial.
Law enforcement agencies typically deal with online fraud and cybercrime, although it depends on where you live. Here is the list of local authority groups that handle incidents like ransomware attacks, sorted by country:
- USA - Internet Crime Complaint Center IC3
- United Kingdom - ActionFraud
- Canada - Canadian Anti-Fraud Centre
- Australia - ScamWatch
- New Zealand - ConsumerProtection
- Germany - Polizei
- France - Ministère de l'Intérieur
If your country is not listed above, you should contact the local police department or communications center.
Isolate the infected computer
Some ransomware strains aim to infect not only one computer but hijack the entire network. As soon as one of the machines is infected, malware can spread via the network and encrypt files everywhere else, including Network Attached Storage (NAS) devices. NAS devices are commonly compromised via reused administrator credentials and remote access services, and attackers may also delete existing snapshots. If your computer is connected to a network, it is important to isolate it to prevent re-infection after ransomware removal is complete.
In modern environments, ransomware often spreads using stolen credentials, remote management tools, VPN connections, and cloud synchronization services, not only through shared network drives.
The easiest way to disconnect a PC from everything is simply to plug out the ethernet cable. This does not disconnect wireless networks, VPN connections, or cloud services, which must also be disabled separately. However, in the corporate environment, this might be extremely difficult to do (also would take a long time). In many organizations, devices are centrally managed, and network isolation is typically performed by IT or security teams using endpoint security or device management tools. The method below will disconnect from all the networks, including local and the internet, isolating each of the machines involved.
On modern Windows systems, network connections can also be disabled through the Settings app or automatically isolated using endpoint detection and response (EDR) tools.
- Type in Control Panel in Windows search and press Enter
- Go to Network and Internet
- Click Network and Sharing Center
- On the left, pick Change adapter settings
- Right-click on your connection (for example, Ethernet), and select Disable
- Confirm with Yes.
If you are using some type of cloud storage you are connected to, you should disconnect from it immediately. It is also advisable to disconnect all the external devices, such as USB flash sticks, external HDDs, etc. Once the malware elimination process is finished, you can connect your computers to the network and internet, as explained above, but by pressing Enable instead. Before reconnecting, credentials should be reset, persistence mechanisms checked, and backups verified to ensure reinfection does not occur.
From our report of Oct 2026 · not reviewed since
Iisa ransomware is the cryptovirus that asks for payment and promises to recover files after the transfer
Iisa virus is an extortion-based program from cybercriminals who are focused on money demands.
The encryption process is used to create issues with the machine, so once the ransom note appears on the screen, victims get straight to payment and think that data can be restored. Unfortunately, files marked with .iisa appendix and made useless, so the payments can be gathered. None of the claims in the ransom note _readme.txt are true.
There are several universal methods for recovering encrypted files, but the creators' decryption tool is most likely not developed or at least not provided for the victims. This is the Djvu ransomware family member, so we have a few tricks for the file recovery below. It is vital to read the entire instruction manual carefully and make sure you understand the risks and the consequences of the infection.
Once the machine is infected with the Iisa virus, it can create major issues when encoding data and running processes are not enough. This threat also adds files on your computer to control persistence while avoiding detection by masquerading as Windows update pop-ups that prompt people for security scans without revealing its true purpose - attacking you from within!
From our report of Oct 2026 · not reviewed since
What do you need to know about ransomware?
The Iisa virus is ransomware that infects your machine and immediately alters files, this nasty program overwrites original content with an encoded version and renames them to include the unique appendix at the file end. Like most types of malware out there today, ransomware is created to make a profit for the developers and associates.
It is always best to avoid these types of situations if possible, but sometimes you can not help it, and the malware finds you.
If this is the case and your computer has been infected with ransomware, some things need immediate attention, like backing up data on an external drive before cutting all ties from other sources. The Iisa ransomware may affect system performance over time, so some steps need to be taken as soon as possible.
Cybercriminals behind the virus can be contacted using manager@mailtemp.ch or helprestoremanager@airmail.cc email address, but you receive the promised decryptor only if you pay them $490/$980. Paying for the decryption software and key can be dangerous. Even though criminals offer the discount for the ransom price it gets bigger after 72 hours without contact from victims. Experts note that it is dangerous and mainly useless to pay.
From our report of Oct 2026 · not reviewed since
The possible decryption for Iisa virus
This dangerous ransomware is a version of the Djvu ransomware that releases version after version weekly.
The previously known variants were easily decryptable, but the Iisa ransomware is not because of the altered encryption process and method. These newer versions use the online ID forming method that means each affected device gets the one-of-a-kind key needed for the decryption.
Previously offline id method allowed many victims to get their files restored with one key obtained from the victim. Right now, all the variants of the family are non-decryptable because of the changes made in 2019.
If your computer got infected with one of the Djvu variants, you should try using Emsisoft decryptor for Djvu/STOP. It is important to mention that this tool will not work for everyone - it only works if data was locked with an offline ID due to malware failing to communicate with its remote servers.
Even if your case meets this condition, somebody from the victims has to pay criminals, retrieve an offline key, and then share it with security researchers at Emsisoft. As a result, you might not be able to restore the encrypted files immediately.
Thus, if the decryptor says your data was locked with an offline ID but cannot be recovered currently, you should try later. You also need to upload a set of files - one encrypted and a healthy one to the company's servers before you proceed.
From here, there are three available outcomes:
- After pressing the Download button, a small pop-up at the bottom, titled decrypt_STOPDjvu.exe should show up - click it.
- If User Account Control (UAC) message shows up, press Yes.
- Agree to License Terms by pressing Yes.
- After Disclaimer shows up, press OK.
- The tool should automatically populate the affected folders, although you can also do it by pressing Add folder at the bottom.
- Press Decrypt.
- "Decrypted!" will be shown under files that were decrypted successfully - they are now usable again.
- "Error: Unable to decrypt file with ID:" means that the keys for this version of the virus have not yet been retrieved, so you should try later.
- "This ID appears to be an online ID, decryption is impossible" - you are unable to decrypt files with this tool.
From our report of Oct 2026 · not reviewed since
Steps of getting the system back to safety
Cybercriminals use Trojans or malicious emails to distribute their malware payload.
Emails can be distributed with file attachments as MS files or executables. The threat can be included: inside the file itself (hidden among other code); linked with malicious links in text messages and online ads, even those looking innocent enough.
Malicious files might also arrive via Peer-to-Peer networks like torrent clients, where users infect computers by opening them without realizing what the contents include. This family is known for spreading around its payload with the help of chest for games, cracks for popular software. Malicious software often comes through third-party websites offering free downloads too.
Iisa virus can act in the background immediately after the infiltration. Even though encryption is not the first process, the threat runs on the device. This cryptocurrency extortion virus can create major issues when the machine is infiltrated, and encoded data is not just a problem this threat creates.
Ransomware like this adds various processes on your computer to control its persistence as well avoid detection by masking itself with fake Windows update pop-ups. You need to remove the infection as soon as possible to avoid other issues that the Iisa ransomware virus can create. You can do that with apps like or .
Once a computer is infected with malware, its system is changed to operate differently. For example, an infection can alter the Windows registry database, damage vital bootup, and other sections, delete or corrupt DLL files, etc. Once a system file is damaged by malware, antivirus software cannot do anything about it, leaving it just the way it is.
Consequently, users might experience performance, stability, and usability issues, to the point where a full Windows reinstallation is required.
Therefore, we highly recommend using a one-of-a-kind, patented technology of repair. Not only can it fix virus damage after the infection, but it is also capable of removing malware that has already broken into the system thanks to several engines used by the program.
Besides, the application is also capable of fixing various Windows-related issues that are not caused by malware infections, for example, Blue Screen errors, freezes, registry errors, damaged DLLs, etc.
By employing a tool like this, you would not have to worry about future computer issues, as most of them could be fixed quickly by performing a full system scan at any time. Most importantly, you could avoid the tedious process of Windows reinstallation in case things go very wrong due to one reason or another.
- Download the application by clicking on the link above
- Click on the ReimageRepair.exe
- If User Account Control (UAC) shows up, select Yes
- Press Install and wait till the program finishes the installation process.
- The analysis of your machine will begin immediately
- Once complete, check the results - they will be listed in the Summary
- You can now click on each of the issues and fix them manually
From our report of Oct 2026 · not reviewed since
File recovery options
Note that removing the threat is not the same as the decryption, but it is extremely important to clear the system before you attempt any recovery.
Rely on the tools mentioned and remove the Iisa file virus right away, double-check to see if the virus damage is taken care of, and then you can move to the options for file recovery.
There are some different methods for data recovery after ransomware attacks. The decryption tool would be the best, but it is not available right now. Other methods are listed below. Each of these approaches may work in some cases where others fail - following each one closely could save your data from certain losses completely if nothing else can help restore what was lost first.
Since many users do not prepare proper data backups prior to being attacked by ransomware, they might often lose access to their files permanently. Paying criminals behind the Iisa ransomware is also very risky, as they might not fulfill the promises and never send back the required decryption tool.
While this might sound terrible, not all is lost - data recovery software might be able to help you in some situations (it highly depends on the encryption algorithm used, whether ransomware managed to complete the programmed tasks, etc.). Since there are thousands of different ransomware strains, it is immediately impossible to tell whether third-party software will work for you.
Therefore, we suggest trying regardless of which ransomware attacked your computer. Before you begin, several pointers are important while dealing with this situation:
Install data recovery software
The modern world is constantly changing, and because of this, there are many ways for malware to enter your computer. Some examples include email spamming/malicious attachments in emails; by misleading downloads or direct links on websites you visit- even if they seem safe.
Another way that viruses can get inside involves exploiting software vulnerabilities that would allow them access without permission from the owner. There are also many possible ways to get rid of Iisa ransomware, but you need to be sure the threat is eliminated before choosing any of the methods.
Rely on or for help when dealing with an infection like this. Tools like AV-detection-based apps can also prevent virus removal in the first place if used occasionally enough - so don't hesitate to give them a try. Also, do not underestimate the malware and its functions, virus damage, and leftovers can still create issues. Trust the tool for system repair.
- Since the encrypted data on your computer might permanently be damaged by security or data recovery software, you should first make backups of it - use a USB flash drive or another storage.
- Only attempt to recover your files using this method after you perform a scan with anti-malware software.
- Download .
- Double-click the installer to launch it.
- Follow on-screen instructions to install the software.
- As soon as you press Finish, you can use the app.
- Select Everything or pick individual folders where you want the files to be recovered from.
- Press Next.
- At the bottom, enable Deep scan and pick which Disks you want to be scanned.
- Press Scan and wait till it is complete.
- You can now pick which folders/files to recover - don't forget you also have the option to search by the file name!
- Press Recover to retrieve your files.
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.
Make the next attack harmless
Iisa virus could only hurt the files that had no second copy, and the signs (files that end in .iisa and no longer open) showed exactly which ones those were.
The 3-2-1 rule fixes that:
- three copies
- two media
- one disconnected
A practical version for a home PC: OneDrive or another cloud backup with version history, plus an external disk that you plug in once a week for File History and then unplug. Test a restore now and then by opening a few files from the backup on another device.
Details, schedules and what not to back up are in our 3-2-1 backup guide for Windows.
Stream videos without limitations, no matter where you are
There are multiple parties that could find out almost anything about you by checking your online activity.
While this is highly unlikely, advertisers and tech companies are constantly tracking you online. The first step to privacy should be a secure browser that focuses on tracker reduction to a minimum.
Even if you employ a secure browser, you will not be able to access websites that are restricted due to local government laws or other reasons. In other words, you may not be able to stream Disney+ or US-based Netflix in some countries. To bypass these restrictions, you can employ a powerful VPN, which provides dedicated servers for torrenting and streaming, not slowing you down in the process.
Data backups are important - recover your lost files
Ransomware is one of the biggest threats to personal data.
Once it is executed on a machine, it launches a sophisticated encryption algorithm that locks all your files, although it does not destroy them. The most common misconception is that anti-malware software can return files to their previous states. This is not true, however, and data remains locked after the malicious payload is deleted.
While regular data backups are the only secure method to recover your files after a ransomware attack, tools such as can also be effective and restore at least some of your lost data.
Questions about Iisa virus
How do I open .iisa files?
You cannot open them by renaming or with another program, because the content of files ending in .iisa has been encrypted. The only ways back are a working decryptor for the family, or clean copies from elsewhere:
- OneDrive versions
- File History
- an offline backup drive
- Previous Versions if the ransomware did not delete them
Identify the family first by uploading the ransom note and one encrypted file to ID Ransomware or No More Ransom. Avoid websites and programs that promise to open any encrypted file; they do not work and some are scams.
Is there a free Iisa virus decryptor?
We last checked on 6 October 2026, and for Iisa 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 "Iisa 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 Iisa virus get on my computer?
The way Iisa 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 .iisa 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.
Are ransomware recovery services legitimate?
Some are, but read the offer carefully. Genuine data-recovery firms recover deleted originals from disks or rebuild damaged files, and they say so. Others promise to "decrypt any ransomware" for a fixed price, which is impossible without the key; they quietly pay the attackers and keep a margin, sometimes without telling the victim.
Be especially careful with services that contact you after you post about the attack online. Ask for references, a written method and a no-result-no-fee clause, and check the free tools on No More Ransom first.
Did Iisa virus steal my files or passwords?
We do not know yet. Nothing published so far shows data theft by Iisa virus, but the only confirmed sign is files that end in .iisa 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 Iisa 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.
What does _readme.txt tell me about the ransomware?
Quite a lot. The file name _readme.txt, the wording, the contact addresses and the format of the personal ID are typical for each family. Uploading the note together with one encrypted file to ID Ransomware or No More Ransom's Crypto Sheriff usually names the family within seconds.
That name decides your options: some families have free decryptors, some can be partially recovered, and some cannot be decrypted at all. The note's claims about stolen data should be taken seriously but not at face value.
Should I reinstall Windows after the .iisa attack?
Reinstalling removes the ransomware but not the encryption: your files ending in .iisa stay encrypted afterwards. So first copy the encrypted files and the ransom note to a separate drive, in case a decryptor appears later. Then decide:
- a clean-up with an offline scan is often enough for home PCs
- while a full reset is safer if remote access was involved
- scans keep finding new items
Restore your backups only after the PC is clean, and change passwords from another device.
Will Fortect remove Iisa 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 Iisa 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
- Wikipedia: Encryption (read October 6, 2026)
- Virusai: Virusai (read October 6, 2026)
- VirusTotal: iisa detection results (read October 6, 2026)
- CISA: StopRansomware (read October 6, 2026)
- No More Ransom (read October 6, 2026)