CryptoWall 4.0 ransomware: what it is and how to remove it
CryptoWall 4.0 virus is the newest version of CryptoWall ransomware, which is deemed as one of the most destructive computer viruses of all times. Computer users must avoid downloading malicious CryptoWall related files at all costs because hardly anything can be done after such virus steps inside the computer system.
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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CryptoWall 4.0 ransomware: summary
| Detection names | No Microsoft detection name is known |
|---|---|
| Ransom note | HELP_YOUR_FILES.TXT |
| Contact | Not recorded in our earlier report |
| Encrypted file extension | .img |
| 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 9 more facts
| Damage | Not recorded in the old report |
|---|---|
| Name | CryptoWall 4.0 |
| Type | File-encrypting ransomware |
| Symptoms | Files renamed with a new extension and a ransom note left in folders |
| Evidence | One write-up by a security site; no sample analysed yet |
| Encrypted files | .img |
| Free decryptor | No free decryptor is known (checked 6 October 2026) |
| First seen | 2 January 2021 |
| Facts checked | 6 October 2026 |
- File extension:
.img - Note file:
HELP_YOUR_FILES.TXT
From our report of Jan 2021 · not reviewed since
More from our earlier report on CryptoWall 4.0
- Cannot you find the files you need?
- Is the content of the files that you have watched not readable?
- It is normal because the files' names, as well as the data in your files have been encrypted.
- You have become a part of large community CryptoWall.
- [...] For your attention, the software to decrypt the files (as well as the private key that come fitted with it) is a paid product.
How CryptoWall 4.0 ransomware behaves
From our report of Jan 2021 · not reviewed since
Similarities of CryptoWall and CryptoWall 4.0
CryptoWall 4.0 virus is the newest version of CryptoWall ransomware, which is deemed as one of the most destructive computer viruses of all times.
Computer users must avoid downloading malicious CryptoWall related files at all costs because hardly anything can be done after such virus steps inside the computer system. Below is a list of similarities between the first and the fourth versions of CryptoWall:
Unfortunately, trusting cyber-criminals is something that we do not recommend you to do. If you don't want to lose your money, you should NOT pay it because there are thousands of people who decided to pay the ransom but didn't get the decryption key after sending money to hackers.
- Both versions spread via malicious spam emails.
- Interesting fact: CryptoWall variants are created by Russian hackers; therefore, these viruses are designed not to target computers located in Ukraine, Belarus, Kazakhstan, and obviously, Russia. If the virus detects that computer user lives in one of these countries, it automatically destroys itself. If the victim does not live in one of these countries, the virus starts its malicious processes immediately.
- If either the first or the fourth version of CryptoWall enters the computer system, it scans the entire computer system to find all personal user's files. CryptoWall viruses aim to find all data, no matter how valuable it is for the victim, and lock these files using particular encryption algorithms that are nearly impossible to crack.
- After CryptoWall or CryptoWall 4.0 virus finishes the encryption process, it leaves ransom notes on several folders to inform the victim what needs to be done in order to recover the encrypted data.
From our report of Jan 2021 · not reviewed since
CryptoWall 4.0 is definitely one of the worst ransomware-type viruses. How does it work?
To begin with, let us explain what ransomware is.
Ransomware is an extremely dangerous computer virus, which finds and encrypts victim's files stored on the computer and gives no "UNDO" option. In other words, there is hardly any chance to retrieve the files once such virus encrypts them.
That is why it is vital to take precautions before such virus attacks the computer. CryptoWall, CryptoWall 2.0, CryptoWall 3.0 and CryptoWall 4.0 viruses are probably most infamous ransomware-type computer threats that have already affected thousands of computer users.
Ransomware viruses usually encrypt files with such extensions:
- .docx
- .txt
- .img
- .gif
- .mp3
- .mp4
- .flv
Unfortunately, but the latest version of CryptoWall does not only encrypt the data; it can also rename the files. CryptoWall 4.0 replaces file names with random codes, which makes it hard to recognize which files were encrypted. It disables system restore and Windows Startup Repair functions and eliminates volume shadow copies.
Unfortunately, many computer security programs cannot detect this malicious computer threat; it is professionally designed not to be detected by antivirus programs, and it can even avoid detection by the second generation enterprise firewall solutions. Moreover, CryptoWall 4.0 can contaminate the computer with additional malware; in other words, this virus can critically mess up the computer system.
CryptoWall 4.0 uses a complicated encryption technique - it encrypts files using AES cipher first, then it encrypts them using a more powerful RSA cipher. After this ransomware encrypts user's files, it drops ransom notes on each folder that contains encrypted data. Such messages can appear as .txt, .html, or .png files. For example:
These messages include such statements:
As you can see, CryptoWall 4.0 ransomware explains that victim's files were encrypted. It even makes fun of the victim by saying "Congratulations." Then it states that a software that decrypts files is a paid product, and user needs to buy it for 700 US dollars within 96 hours.
Otherwise, the price will raise to 1400 US dollars. You should not believe such promises because there is no guarantee that the cyber criminals will do anything to decrypt your files.
From our report of Jan 2021 · not reviewed since
How could CryptoWall 4.0 infect my computer?
If you do not want to experience data leakage and if you do not wish to lose your files, you should think of possible ways to secure your computer.
It can delete the CryptoWall 4.0 ransomware from your computer. However, once a ransomware encrypts files, it can be very hard or even not possible to recover them. Therefore, you should always keep a backup of your files on an external disk. To find detailed instructions how to remove CryptoWall 4.0, navigate to page 2.
- CryptoWall 4.0, which is also known as HELP_YOUR_FILES virus, just like other versions of CryptoWall is spread via fraudulent e-mail letters. These letters commonly deliver a fake resume and encourage the victim to open it: "Hello, my name is [...] attached is my resume! I would appreciate your cooperation on this matter." This technique can easily deceive people who work in companies that are looking for new employees. Although your email service provider should automatically identify such email as infectious and filter it as Junk/Spam, there is a chance that your e-mail service may not filter it like that. However, you should never open emails from senders that you have never heard of. Such CryptoWall 4.0 e-mails include a text attachment (a fake resume), which is actually a JavaScript file. Once you open it, it downloads and executes the CryptoWall 4.0 virus onto your system.
- CryptoWall 4.0 also spreads via malicious exploit kits (such as Nuclear exploit kit, and Angler exploit kit) which means that cyber-criminals tend to take advantage of outdated software on user's computers and exploit the vulnerabilities of it. Exploit kits are spread via iFrames, malvertising, and can be found on insecure web pages as well. For this reason, you should never browse through high-risk websites, click on suspicious web content, or download files or programs from questionable download sites.
The CryptoWall 4.0 ransomware note
HELP_YOUR_FILES.TXT
HELP_YOUR_FILES.HTML
HELP_YOUR_FILES.PNG
How to remove CryptoWall 4.0 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 CryptoWall 4.0 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
CryptoWall 4.0 encrypts everything it can reach, including drives and shares you connect later. Cut the network first: cable out, or Wi-Fi off from the taskbar.
Then unplug every USB stick and backup disk and pause cloud sync, so the encrypted versions do not replace your online copies. Do not reconnect any of them until the ransomware is removed from the Windows 11 or Windows 10 PC.
Windows 11: turn off Wi-Fi to take the PC offline. Full procedure with screenshots: Ransomware: first steps, finding a decryptor and recovering files
Step 2: Save the ransom note and confirm the family
Copy
HELP_YOUR_FILES.TXTand one or two files ending in.imgto a USB stick, and leave the originals where they are.From another device, upload the note and a sample file to ID Ransomware or No More Ransom's Crypto Sheriff, which name the family from the note, the extension and the file structure.
Write down the contact address and your personal ID from the note, because a decryptor or the police may ask for them.
Warning: Never contact the attackers from the infected Windows 11 or Windows 10 PC.
Windows 11: the ransom note and encrypted files to copy for identification. Full procedure with screenshots: Ransomware: first steps, finding a decryptor and recovering files
Step 3: Check for a free decryptor
For CryptoWall 4.0, no free decryptor is known (checked 6 October 2026). Search the family name in the No More Ransom decryption tools list and in the free decryptors of Emsisoft, Avast and Kaspersky, because new tools appear years after an attack.
Important: Keep the encrypted files even if nothing works today, and do not pay before every free option is ruled out: payment does not guarantee a working key.
Decryptors run on Windows 11 and Windows 10, but only after the ransomware itself is removed.
Full procedure with screenshots: Ransomware: first steps, finding a decryptor and recovering files
Step 4: Remove the ransomware before you restore or decrypt
Restoring or decrypting files while CryptoWall 4.0 still runs lets it encrypt them again. Run a Full scan in Windows Security > Virus & threat protection > Scan options, then the Microsoft Defender Antivirus (offline scan).
If the ransomware blocks Windows Security, start Safe Mode with Networking and scan from there. Some families install a password stealer as well, so let both scans finish on Windows 11 or Windows 10.
Windows 11: Windows Security > Virus & threat protection > Scan options. Full procedure with screenshots: Run a Microsoft Defender Offline scan
Step 5: Look for shadow copies of the files
Open Command Prompt as administrator and run
vssadmin list shadows. If it lists copies dated before the attack, right-click a folder with encrypted files in File Explorer, choose Properties > Previous Versions, and open or restore a version from before that date.ShadowExplorer, a free tool, shows the same copies when the tab is empty or hidden. Most current families delete shadow copies, so an empty list is normal, but the check takes two minutes on Windows 11 or Windows 10.
Windows 11: vssadmin list shadows shows whether shadow copies exist. Full procedure with screenshots: Ransomware: first steps, finding a decryptor and recovering files
Step 6: Restore the files from a backup or recover deleted originals
Restore from an external backup, File History or OneDrive's version history, choosing a date before the attack. Connect the backup drive only after the scans are clean, or the ransomware encrypts it too.
If there is no backup, file recovery software can sometimes find the deleted originals, because some ransomware writes an encrypted copy and deletes the original file.
Stop writing to the drive and try recovery on Windows 11 or Windows 10 before new files overwrite the space.
Full procedure with screenshots: Recover deleted files (Recycle Bin, backups, OneDrive) On uGetFix
Instructions for each browser and system
The detailed steps for every browser and system this guide covers. Open the one you use.
Manual removal using Safe Mode
Important! →
Manual removal guide might be too complicated for regular computer users. It requires advanced IT knowledge to be performed correctly (if vital system files are removed or damaged, it might result in full Windows compromise), and it also might take hours to complete. Therefore, we highly advise using the automatic method provided above instead.
Step 1. Access Safe Mode with Networking
Manual malware removal should be best performed in the Safe Mode environment.
Windows 7 / Vista / XP
- Click Start > Shutdown > Restart > OK.
- When your computer becomes active, start pressing F8 button (if that does not work, try F2, F12, Del, etc. - it all depends on your motherboard model) multiple times until you see the Advanced Boot Options window.
- Select Safe Mode with Networking from the list.
Windows 10 / Windows 8
- Right-click on Start button and select Settings.
- Scroll down to pick Update & Security.
- On the left side of the window, pick Recovery.
- Now scroll down to find Advanced Startup section.
- Click Restart now.
- Select Troubleshoot.
- Go to Advanced options.
- Select Startup Settings.
- Press Restart.
- Now press 5 or click 5) Enable Safe Mode with Networking.
Step 2. Shut down suspicious processes
Windows Task Manager is a useful tool that shows all the processes running in the background. If malware is running a process, you need to shut it down:
- Press Ctrl + Shift + Esc on your keyboard to open Windows Task Manager.
- Click on More details.
- Scroll down to Background processes section, and look for anything suspicious.
- Right-click and select Open file location.
- Go back to the process, right-click and pick End Task.
- Delete the contents of the malicious folder.
Step 3. Check program Startup
- Press Ctrl + Shift + Esc on your keyboard to open Windows Task Manager.
- Go to Startup tab.
- Right-click on the suspicious program and pick Disable.
Step 4. Delete virus files
Malware-related files can be found in various places within your computer. Here are instructions that could help you find them:
- Type in Disk Cleanup in Windows search and press Enter.
- Select the drive you want to clean (C: is your main drive by default and is likely to be the one that has malicious files in).
- Scroll through the Files to delete list and select the following:
Temporary Internet Files
Downloads
Recycle Bin
Temporary files - Pick Clean up system files.
- You can also look for other malicious files hidden in the following folders (type these entries in Windows Search and press Enter):
%AppData%
%LocalAppData%
%ProgramData%
%WinDir%
After you are finished, reboot the PC in normal mode.
From our report of Jan 2021 · not reviewed since
How to remove this virus and fix my computer?
Speaking of ransomware, it is right to say that prevention is better than the cure.
If you can see that all your files were renamed and that you cannot open them anymore, also if you have spotted files named as HELP_YOUR_FILES.TXT, HELP_YOUR_FILES.HTML, HELP_YOUR_FILES.PNG and similar names, it means that you have become a victim of CryptoWall 4.0 virus.
This virus is categorized as ransomware which means that it seeks to make you pay a ransom in exchange for the decryption key that is needed to unlock the data. However, there is no guarantee that you will receive it after doing what hackers command you to do.
All removal instructions that should help you to fix your computer are provided below this article. Remember to be very cautious while browsing on the web - do not open suspicious e-mail attachments and do not surf through untrustworthy websites. There are a lot of cyber-criminals working hard these days, so be careful and do not become another cybercrime victim.
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
CryptoWall 4.0 could only hurt the files that had no second copy, and the signs (files that end in .img 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.
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 CryptoWall 4.0 ransomware
How do I open .img files?
You cannot open them by renaming or with another program, because the content of files ending in .img 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.
How did CryptoWall 4.0 get on my computer?
The way CryptoWall 4.0 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 .img 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 CryptoWall 4.0 steal my files or passwords?
We do not know yet. Nothing published so far shows data theft by CryptoWall 4.0, but the only confirmed sign is files that end in .img 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 CryptoWall 4.0 decryptor?
We last checked on 6 October 2026, and for CryptoWall 4.0 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 "CryptoWall 4.0 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.
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.
Is CryptoWall 4.0 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 delete HELP_YOUR_FILES.TXT?
Yes, the note itself is harmless text and deleting it does not affect your files. Keep at least one copy first, outside the infected PC. HELP_YOUR_FILES.TXT contains your personal ID and the attackers' contact details, which identification services use to tell which family encrypted your files, and which a decryptor may need later.
Police reports also ask for it. Once you have saved a copy, you can remove the notes from every folder after the ransomware program has been removed and your files are restored or backed up.
Will .img spread to my other drives?
It can. Ransomware encrypts every drive and network share it can reach while it runs, so external disks, USB sticks and shared folders connected during the attack may also have files ending in .img. Disconnect everything now, then check each device from a clean computer.
Do not plug a backup drive into the infected PC until the ransomware has been removed with an offline scan. Cloud folders such as OneDrive sync the encrypted versions, but they keep earlier versions you can usually restore.
Will Fortect remove CryptoWall 4.0?
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 CryptoWall 4.0, 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
- CISA: StopRansomware (read October 6, 2026)
- No More Ransom (read October 6, 2026)
- FTC: How to recognize, remove and avoid malware (read October 6, 2026)
- Microsoft Learn: Microsoft Defender Offline (read October 6, 2026)
- Microsoft Learn: How Microsoft names malware (read October 6, 2026)