Cuag ransomware: what it is and how to remove it
When the infection starts the infiltration, users might not notice any strange activities, but the Cuag file virus manages to damage the processes, programs on the machine and directly affect the stage of commonly used files. This is a really malicious and dangerous cyber threat.
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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Cuag ransomware: summary
| Distribution | Files attached to emails can have ransomware payload, pirating platforms are known for distributing threats during installs of various games and software |
|---|---|
| Name | Cuag ransomware |
| Type | File-locker, cryptovirus |
| File marker | .cuag |
| Ransomware family | Djvu ransomware |
| Contact emails | support@sysmail.ch, helprestoremanager@airmail.cc |
| 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
| Ransom note | _readme.txt; the text of the note is not in our records |
|---|---|
| Ransom amount | Starts with $490 as a discount. Goes up to $980 |
| Detection names | No Microsoft detection name is known |
| Encrypted file extension | .cuag |
| 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 | .cuag |
| Attacker contacts | support@sysmail.ch |
| Free decryptor | No free decryptor is known (checked 7 October 2026) |
| First seen | 7 February 2022 |
| Facts checked | 7 October 2026 |
- File extension:
.cuag - Note file:
_readme.txt - Contact:
support@sysmail.ch
From our report of Feb 2022 · not reviewed since
Cuag ransomware is a malicious program designed to demand money from the virus victims
When the infection starts the infiltration, users might not notice any strange activities, but the Cuag file virus manages to damage the processes, programs on the machine and directly affect the stage of commonly used files. This is a really malicious and dangerous cyber threat.
Once inside the system, it encrypts all personal pictures videos documents archives, or other files by using an encryption algorithm that also appends a unique .cuag extension to each encrypted file's name.
The process makes all data unreadable by anyone except those who have the key which is in possession of criminals behind this ransomware attack. This information can be found within the _readme.txt file placed on the desktop and in other folders.
There are many different types of malware that can affect your computer. One of the most dangerous types is ransomware that this Cuag virus is. It will encrypt all files on the victim's device and provide the information with an intimidating message demanding money in return for the decryption.
This cryptovirus was created specifically as a means to take financial advantage of people. The threat actors ask for a payment of Bitcoin that is starting with $490 and come up to $980.
You are advised to avoid paying the requested fee because there's always hope for restoration even without purchasing some kind of software or key from criminals who will only keep on promises but never deliver anything. The official decryption tool is not available, so it is not easy to achieve full file recovery, but removing the infection is crucial here.
When the virus locks down your device, it will encrypt all files and it comes out of nowhere. The threat can come when users download and open cracked or pirated software. They are activating a virus that can affect their system's performance significantly.
This is because of how the encryption process works alongside other functions conducted by cryptomalware. Cuag file viruses can damage files, functions, and other programs for the sake of virus detection avoidance. It ensures the persistence to keep the machine running the threat and additional infections.
From our report of Feb 2022 · not reviewed since
More from our earlier report on Cuag ransomware
- You need tools like or for the proper ransomware removal, so run the full system scan and remove the infection properly
- Threats affect more than common files because the infection manages to alter files and system functions, run the tool for the remediation on the machine
How Cuag ransomware behaves
From our report of Feb 2022 · not reviewed since
The family of dangerous ransomware
The developers of this nasty file-locking parasite want to persuade you that the only way to regain access is by purchasing their decryption software.
And they're trying really hard to convince. The discount is offered for the first 72 hours after the Cuag ransomware encryption process.
Cryptovirus belongs to the malware family known as STOP virus and is derived from Djvu ransomware virus directly. This malicious software encrypts files since 2018 and changes introduced in August 2019 make the threat not decryptable, unfortunately. It is a bummer for victims, but there are alternate options that we list through the article.
These decryption options depend on the encryption keys and IDs formed during the process. The latest versions like the Cuag file virus, use the online IDs that are formed precisely for each different device that is affected. This way the decryption is only possible when the key is obtained by law enforcement or after payment.
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 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.
The Cuag ransomware note
The note is called _readme.txt.
We did not record the full text of the ransom note in our report.
How to remove Cuag 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 Cuag 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 Cuag 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
.cuagand 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 Cuag ransomware, no free decryptor is known (checked 7 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 Cuag 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 Cuag 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.
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.
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.
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.
From our report of Feb 2022 · not reviewed since
Removing the infection and restoring the performance of the machine
Experts recommend not paying the ransom, as cybercriminals might not keep their promises.
Different ransomware is rapidly infecting computers after encrypting users' files. Some types of malware are practically impossible to eliminate without specific tools or options for data recovery. Others can be removed using regular antivirus software like or .
You should base this tool selection on the fact that mainly this family is detected by various AV tools and can be terminated using a security application like this when the system is fully scanned and checked for malicious pieces. You can find additional issues on the system not only the ransomware, so make sure to remove all the listed programs from the device.
These applications can help eliminate the threat and all its files or related programs. It is up to the cybercriminal whether they will provide the necessary tool or not. This is why it's best not to trust criminals and pay ransoms that can cost thousands of dollars. You can remove the infection fully and then worry about those affected files.
Cuag virus can be exceptionally dangerous if you do not react as soon as possible. The demand for $980 or $490 in Bitcoin with the discount can look manageable when your files are valuable. However, you should never consider payment as the best option for this infection and data recovery. If you contact criminals via support@sysmail.ch, helprestoremanager@airmail.cc, you get another infection instead of the decryption tool or any other help.
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 reinstallation is required.
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.
File encryption and Cuag ransomware infection are two independent processes, but cryptocurrency extortion happens when there is a virus running in your operating system. The same goes for file recovery and virus removal. Threat actors have the option of blackmailing you because they can make changes within the system. You need to terminate the infection and then can repair files with options available to you.
You should copy the encrypted files onto a separate medium, such as a USB flash drive or SSD, and then disconnect them. Encrypted data does not hold any malicious code so it's safe to transfer between devices.
Then you can wait for some decryption tool developments later. The Cuag ransomware virus infection has caused issues. The threat may also lock down various applications needed for data recovery and system functions.
- 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
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 Cuag 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 .cuag and no longer open.
Setting it up step by step: 3-2-1 backups on Windows 11 and 10.
Choose a proper web browser and improve your safety with a VPN tool
Online spying has got momentum in recent years and people are getting more and more interested in how to protect their privacy online.
One of the basic means to add a layer of security - choose the most private and secure web browser. Although web browsers can't grant full privacy protection and security, some of them are much better at sandboxing, HTTPS upgrading, active content blocking, tracking blocking, phishing protection, and similar privacy-oriented features.
However, if you want true anonymity, we suggest you employ a powerful VPN - it can encrypt all the traffic that comes and goes out of your computer, preventing tracking completely.
Lost your files? Use data recovery software
While some files located on any computer are replaceable or useless, others can be extremely valuable.
Family photos, work documents, school projects - these are types of files that we don't want to lose. Unfortunately, there are many ways how unexpected data loss can occur:
- power cuts
- Blue Screen of Death errors
- hardware failures
- crypto-malware attack
- even accidental deletion
To ensure that all the files remain intact, you should prepare regular data backups. You can choose cloud-based or physical copies you could restore from later in case of a disaster. If your backups were lost as well or you never bothered to prepare any, can be your only hope to retrieve your invaluable files.
Questions about Cuag ransomware
Should I pay the ransom in _readme.txt?
Not before you have tried everything else. Identify the family from _readme.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 .cuag files?
You cannot open them by renaming or by choosing another program. The .cuag ending shows that Cuag 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 Cuag ransomware. Store the encrypted files on an external disk until then.
Did Cuag ransomware steal my files or passwords?
We do not know yet. Nothing published so far shows data theft by Cuag ransomware, but the only confirmed sign is files that end in .cuag 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 there a free Cuag ransomware decryptor?
We last checked on 7 October 2026, and for Cuag 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 "Cuag 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 Cuag ransomware get on my computer?
The way Cuag 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 .cuag 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.
Is Cuag 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 .cuag from the file names?
You can try it on a copy, but for real ransomware it will not help. The .cuag 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 _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.
Will Fortect remove Cuag 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 Cuag 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
- Zondervirus: Zondervirus (read October 7, 2026)
- VirusTotal: Virus sample (read October 7, 2026)
- CISA: StopRansomware (read October 7, 2026)
- No More Ransom (read October 7, 2026)
- FTC: How to recognize, remove and avoid malware (read October 7, 2026)