Sigrun ransomware: what it is and how to remove it
Sigrun is a ransomware virus that was discovered by security researchers in the middle of May 2018. Malware enters machine unnoticed, executes its payload and then locks up all audio, video, picture, text, database and other personal files.
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.
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Sigrun ransomware: summary
| Detection names | No Microsoft detection name is known |
|---|---|
| Ransom note | RESTORE-SIGRUN.txt |
| Contact | sigrun_decryptor@protonmail.ch |
| Encrypted file extension | .sigrun |
| Decryptor | No free decryptor is known for this variant; check No More Ransom (nomoreransom.org) for updates |
| Distribution | Not recorded in the old report |
| 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 10 more facts
| Damage | Not recorded in the old report |
|---|---|
| Name | Sigrun ransomware |
| Type | File-encrypting ransomware |
| 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 | .sigrun |
| Attacker contacts | sigrun_decryptor@protonmail.ch |
| Free decryptor | No free decryptor is known (checked 6 October 2026) |
| First seen | 28 June 2021 |
| Facts checked | 6 October 2026 |
- File extension:
.sigrun - Note file:
RESTORE-SIGRUN.txt - Contact:
sigrun_decryptor@protonmail.ch
From our report of Jun 2021 · not reviewed since
More from our earlier report on Sigrun ransomware
- Spam emails, fake downloads, repacked software installers, etc.
- Use reputable security software or
- System functions require additional help from tools like
The Sigrun ransomware note
Dear user, all your important files have been encrypted! Don't worry! Your files still can be restored by us! In order to restore it you need to contact with us via e-mail.
sigrun_decryptor@protonmail.ch
As a proof we will decrypt 3 files for free! Please, attach this to your message:
How to remove Sigrun ransomware
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 Sigrun ransomware 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 Sigrun ransomware 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
.sigrunand the instructions are inRESTORE-SIGRUN.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 Sigrun ransomware, 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 Sigrun ransomware 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 Sigrun ransomware 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.
Repair damaged system components
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 is not capable of doing 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 reinstall 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.
- 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
- If you see many problems that you find difficult to fix, we recommend you purchase the license and fix them automatically.
By employing , 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.
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.
Restore files using data recovery software
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 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:
- 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.
Install data recovery 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.
Find a working decryptor for your files
File encryption is a process that is similar to applying a password to a particular file or folder. However, from a technical point of view, encryption is fundamentally different due to its complexity. By using encryption, threat actors use a unique set of alphanumeric characters as a password that can not easily be deciphered if the process is performed correctly.
There are several algorithms that can be used to lock data (whether for good or bad reasons); for example, AES uses the symmetric method of encryption, meaning that the key used to lock and unlock files is the same. Unfortunately, it is only accessible to the attackers who hold it on a remote server - they ask for a payment in exchange for it. This simple principle is what allows ransomware authors to prosper in this illegal business.
While many high-profile ransomware strains such as Djvu or Dharma use immaculate encryption methods, there are plenty of failures that can be observed within the code of some novice malware developers. For example, the keys could be stored locally, which would allow users to regain access to their files without paying. In some cases, ransomware does not even encrypt files due to bugs, although victims might believe the opposite due to the ransom note that shows up right after the infection and data encryption is completed.
Therefore, regardless of which crypto-malware affects your files, you should try to find the relevant decryptor if such exists. Security researchers are in a constant battle against cybercriminals. In some cases, they manage to create a working decryption tool that would allow victims to recover files for free.
Once you have identified which ransomware you are affected by, you should check the following links for a decryptor:
- No More Ransom Project
- Free Ransomware Decryptors by Kaspersky
- Free Ransomware Decryption Tools from Emsisoft
- Avast decryptors
If you can't find a decryptor that works for you, you should try the alternative methods we list below. Additionally, it is worth mentioning that it sometimes takes years for a working decryption tool to be developed, so there are always hopes for the future.
Create data backups to avoid file loss in the future
Scan your system with anti-malware
If you are a victim of ransomware, you should employ anti-malware software for its removal. Some ransomware can self-destruct after the file encryption process is finished. Even in such cases, malware might leave various data-stealing modules or could operate in conjunction with other malicious programs on your device.
or can detect and eliminate all ransomware-related files, additional modules, along with other viruses that could be hiding on your system. The security software is really easy to use and does not require any prior IT knowledge to succeed in the malware removal process.
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 Jun 2021 · not reviewed since
Sigrun is a file-locking ransomware that demands ransom in Dash or Bitcoin for file decryption
Sigrun is a ransomware virus that was discovered by security researchers in the middle of May 2018.
Malware enters machine unnoticed, executes its payload and then locks up all audio, video, picture, text, database and other personal files. It uses complicated cryptography to add a .sigrun file extension, making all data unusable.
The virus drops ransom note into each of the "RESTORE-SIGRUN.txt" into each of the infected folders and also opens up a browser tab with the same message in .html format. Users are asked to contact hackers via sigrun_decryptor@protonmail.ch in order to get their files back. Victims are asked to pay up to $2,500 in Dash or Bitcoin cryptocurrency, although Russians can get a decryptor for free.
It is interesting how ransomware authors are going for Norse mythology as Sigrun means "victory rune" and is a valkyrie - a mythological angel-like creature. Nevertheless, the authors of the ransomware are of Russian origin due to the fact that they try to avoid infecting Russian individuals.
The file-locking virus spreads via contaminated attachments in spam emails. Users who open the .txt, .pdf, .doc, .zip, or other affixed files instantaneously download malware into their computers. It is then ready to start its malicious activities.
First, the crypto-virus modifies certain system files (including registry entries) to acquire boot persistence. This way, it can start up every time Windows is launched. Next, it initiates a full system scan to find files to lock up. As soon it is complete, Sigrun malware encrypts data and executes the ransom notes to inform the user about the situation.
Various file types are targeted by the virus, including .txt, .doc, .html, .xlsx, .dat, .mp3, .jpg. .gif and similar. For example, the encoded file would look like this: picture.jpg.sigrun. The strong encryption algorithm is used for file encryption, and only a key can unlock them.
These decryptors are usually stored on a remote server and are only accessible to hackers. Nevertheless, users should ignore the key - remove the ransomware first and then proceed with file recovery.
There are several files that the virus does not targets, including:
Users are urged to contact criminals via the sigrun_decryptor@protonmail.ch address. The size of ransom is unknown, and it seems like hackers communicate with the victim before agreeing on the size of the payment. It is typically demanded in Bitcoin or another popular cryptocurrency, like Monero or Ethereum. Victims are also offered the proof that decryption is possible - they can send authors three files which they would decode for free.
The note states the following:
As we already mentioned, cybercriminals should be ignored as they often do not provide the offered key. Besides, even if they do, they will know that you are susceptible to the demands and might contaminate your machine again in the future. Instead, reboot your PC in Safe Mode with Networking and take care of Sigrun removal. Security experts suggest using or for that task.
If you have a backup ready - you are lucky, as you can recover all your files without problems, as long as they are stored on a remote server and not connected to the contaminated machine. If you are not that prepared and didn't use data backup, you might be in a bit of trouble. However, you can always try third-party tools that may help you with file recovery.
- .sigrun
- .admin
- .dll
- .sys
- .exe
- .ico
- .key, etc.
From our report of Jun 2021 · not reviewed since
Hackers help Russian victims for free
Russian cybercriminals are known to avoid infecting Russian-speaking individuals (including former USSR countries), as they are cautious of the authorities, who could target them if locals were involved.
When Sigrun is first executed, it checks for the keyboards layouts installed - "HKEY_CURRENT_USER\Keyboard Layout\Preload." Once the virus finds the Russian layout, it does not encrypt files and merely deletes itself. However, not all former USSR countries use the Russian layout; therefore, those individuals can still get infected. Hackers also mentioned that they added a Ukrainian layout to the list of exceptions.
While authors of Sigrun virus ask for as much as $2,500 in Dash or Bitcoin for file decryption, all Russian-speaking users have to do is email culprits and they offer their help for free.
From our report of Jun 2021 · not reviewed since
Avoid deadly ransomware viruses by deleting spam emails
The best practice is not to contaminate your machine with viruses in the first place.
Of course, there will never be a guarantee as malware authors continually modify their code to improve avoidance and develop their malicious software distribution methods. However, there is something you can do. You can be more careful and attentive while browsing the internet.
First of all, we suggest using strong passwords for each of your accounts and change them regularly. Note that unprotected RDP configuration or weak passwords might be an easy way for hackers to infiltrate your machine with malware.
Next, you should not open spam emails carelessly. Malicious attachments often hide inside these emails, as well as cleverly-disguised hyperlinks may lead you to malicious payload execution.
Therefore, if in doubt, make sure you delete the message even without looking at it. Beware that some criminals have decent social engineering skills and are great at luring people with perfectly constructed phishing emails.
Finally, avoid suspicious websites, especially cracked software and other file-sharing sites. Additionally, do not click on questionable ads as they might lead you to malware-ridden sites.
From our report of Jun 2021 · not reviewed since
Sigrun virus elimination procedure
Remember, you have to remove Sigrun ransomware before you proceed with file recovery.
Otherwise, your data will be contaminated and locked up again. If you have remote storage with a backup ready, do not connect it to your machine before you are sure that the virus is exterminated.
Malware can be eliminated using anti-malware tools that have the power to find the pieces of ransomware and other payload pieces. You need tools like or to fully eliminate the infection. Otherwise, you risk getting files affected again.
Ransomware viruses are serious threats and use sophisticated code. Thus, do not even try manual Sigrun removal as you will fail. Only trained professionals can execute that task.
Instead, employ reputable security software, enter Safe Mode with Networking, and perform a full system scan. If you did not have a backup, check out the alternative file restoration methods below.
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 Sigrun ransomware 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 .sigrun and no longer open.
Setting it up step by step: 3-2-1 backups on Windows 11 and 10.
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 Sigrun ransomware
Should I pay the ransom in RESTORE-SIGRUN.txt?
Not before you have tried everything else. Identify the family from RESTORE-SIGRUN.txt and one encrypted file, check No More Ransom for a free decryptor, and look for clean copies in OneDrive, backups and Previous Versions.
Paying funds further attacks, may be illegal if the group is sanctioned, and is no promise of a working key: many victims get partial or broken decryption. If you consider paying for business-critical data, involve the police and a professional incident responder first, and never pay through intermediaries who promise their own decryption.
How do I open .sigrun files?
You cannot open them by renaming or by choosing another program. The .sigrun ending shows that Sigrun ransomware 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 Sigrun ransomware. Store the encrypted files on an external disk until then.
Is there a free Sigrun ransomware decryptor?
We last checked on 6 October 2026, and for Sigrun ransomware 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 "Sigrun ransomware 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.
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 did Sigrun ransomware get on my computer?
The way Sigrun ransomware 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 .sigrun 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 Sigrun ransomware steal my files or passwords?
We do not know yet. Nothing published so far shows data theft by Sigrun ransomware, but the only confirmed sign is files that end in .sigrun 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 Sigrun ransomware 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 .sigrun from the file names?
You can try it on a copy, but for real ransomware it will not help. The .sigrun 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 RESTORE-SIGRUN.txt tell me about the ransomware?
Quite a lot. The file name RESTORE-SIGRUN.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.
Will Fortect remove Sigrun ransomware?
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 Sigrun ransomware, 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
- Twitter: Sigrun Ransomware (read October 6, 2026)
- LosVirus: LosVirus (read October 6, 2026)
- Webroot: What is Social Engineering? (read October 6, 2026)
- CISA: StopRansomware (read October 6, 2026)
- No More Ransom (read October 6, 2026)