EncoderCSL ransomware: what it is and how to remove it
EncoderCSL ransomware is a HiddenTear-based file locking malware that was first spotted by multiple security researchers in mid-February 2020. Once inside the system, the virus applies the AES encryption algorithm to lock a limited number of files located on the system, which appends the .locked extension to them as well.
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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EncoderCSL ransomware: summary
| Name | EncoderCSL ransomware |
|---|---|
| Type | File locking virus, cryptomalware |
| Based on | HiddenTear |
| Main executable | EncoderCSL.exe, or another random name |
| File extension | Each .txt and .test file on the system is appended with .locked extension; for example, a "data.txt" file is turned into "data.txt.locked" |
| Encryption method | A symmetric encryption algorithm is used – AES (Advanced Encryption Standard) |
| 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 17 more facts
| Ransom notes | A pop-up message asks victims to view the READ.txt or READ_IT.txt files, but they are currently not dropped on the computer during the infection process |
|---|---|
| File recovery | Retrieving personal files without backups is almost impossible unless you were lucky enough and the malware failed to delete Shadow Volume Copies; additionally, in some cases, data recovery software might be able to recover at least some of encrypted files |
| Malware removal | Perform a full system scan with a security program that can recognize the threat |
| Detection names | No Microsoft detection name is known |
| Contact | Not recorded in our earlier report |
| Encrypted file extension | .locked |
| Decryptor | No free decryptor is known for this variant; check No More Ransom (nomoreransom.org) for updates |
| Distribution | Not recorded in the old report |
| Damage | Not recorded in the old report |
| Symptoms | Files renamed with a new extension, a ransom note left in folders and a Windows Security "Threats found" notification |
| Evidence | 5 write-ups by security sites; no sample analysed yet |
| Encrypted files | .locked |
| Ransom note | READ.txt |
| Free decryptor | No free decryptor is known (checked 6 October 2026) |
| First seen | 24 February 2020 |
| Microsoft Defender name | Ransom:Win32/HiddenTear.gen |
| Facts checked | 6 October 2026 |
EncoderCSL ransomware detection names
If Windows Security shows Ransom:Win32/HiddenTear.gen, it has found EncoderCSL ransomware or a file that belongs to it.
Write the name down before you click Remove: it is the most useful search term later, and you will need it if you report the incident.
A family name in the label is more informative than a heuristic one. Our page on why one threat has many antivirus names lists the common formats and what each part means.
- File extension:
.locked - Note file:
READ.txt
How EncoderCSL ransomware behaves
From our report of Feb 2020 · not reviewed since
EncoderCSL ransomware is a data-locker that targets files with .txt and .test extensions on your computer
EncoderCSL ransomware is a HiddenTear-based file locking malware that was first spotted by multiple security researchers in mid-February 2020.
Once inside the system, the virus applies the AES encryption algorithm to lock a limited number of files located on the system, which appends the .locked extension to them as well. EncoderCSL ransomware virus currently only locks .txt and .test files on the host system, which is a clear indication that the malware is still in the experimental stage (fully functional ransomware usually targets all personal data).
After the encryption process, the EncoderCSL virus may drop one of the following ransom notes: READ.txt or READ_IT.txt, although this action is not fully functional yet - experts reported that the malware fails to deliver these text files.
Nevertheless, it also displays a pop-up window, which explains why the files were compromised, and also states that victims should not attempt to recover the data without acquiring EncoderCSL ransomware decryptor for the hackers. Even if desired so, reaching criminals is impossible, as no contact details are provided.
Because the prevalence of EncoderCSL ransomware is relatively low, it is unknown what type of tactics threat actors use to distribute the malware. Nevertheless, the most common techniques include:
Once inside the system, EncoderCSL ransomware places its main executable (can be named as anything, although researchers found the "EncoderCSL.exe" in the wild) into the %Temp%, %Users%, or Desktop location and the begins the infection routine.
During this time, the malware deletes Shadow Volume Copies to prevent victims from recovering from the damages quickly, modifies the Windows registry to establish persistence, starts the "LocalSystem" service, loads several modules, reads computer information, etc.
Finally, EncoderCSL ransomware performs file encryption that only affects .txt and .test files - this will append the .locked extension to these file types. The .locked marker has been extensively used by various other Hidden Tear versions, as it is a default market that indicates which files have been compromised.
After the encryption process, EncoderCSL ransomware will display a pop-up message with the following text:
As evident, EncoderCSL ransomware virus developers are not native English language users, although guessing the origin of these people is impossible. Regardless of that, contacting them is impossible anyways, as they do not provide contact details, as there are supposed to be included within the text file on the desktop - it is nowhere to be found.
Even if the ransom note would provide the contact details, security experts highly discourage users from paying the ransom, as victims may get scammed and never received the promised decryption tool. If you had no backups to restore your data, you could try using alternative solutions listed in our recovery section below.
- Malicious spam email attachments or hyperlinks;
- Software vulnerabilities and exploits;
- Poorly protected Remote Desktop connections;
- Pirated program installers and software cracks/keygens;
- Fake update prompts and other fake messages, etc.
From our report of Feb 2020 · not reviewed since
The legacy of HiddenTear: malicious actors keep abusing the open-source project
HiddenTear is a notorious open-source project that was developed by a researcher from Turkey back in 2015.
Since then, the code was leaked, and malicious actors quickly learned how to utilize it for illegal monetization purposes. Even many years after its release, various threat actors may attempt to modify the code and start distributing it using various methods, as it happened with EncoderCSL ransomware.
Nevertheless, the EncoderCSL virus is in the early development stage, as it does not match the criteria of fully functional ransomware just yet. Those infected, however, might lose all the encrypted files forever, as there is no way to contact malicious actors at present.
EncoderCSL ransomware removal is necessary, however, as the improved versions might be employed by authors in the future, applying a fully-working encryption function. In such a case, victims may not only lose their .txt or .test files, but also pictures, videos, music, documents, databases, PDF, and other data.
To remove EncoderCSL ransomware from the system, users need to scan their machines with anti-malware software that is capable of detecting and eliminating the threat automatically. According to Virus Total results, more than 40 different anti-malware engines recognize the main executable as follows:
Nevertheless, we strongly advise you to make a copy of encrypted files before you get rid of the EncoderCSL virus, as its termination might permanently damage the data.
- Ransom:Win32/HiddenTear.gen
- Gen:Variant.MSILPerseus.179410
- A Variant Of MSIL/Filecoder.AK
- Win32:Trojan-gen
- Trojan /Win32.HiddenTear
- MSIL/Filecoder.AK!tr.ransom
- RDN/Ransom
- Mal/Generic-S, etc.
From our report of Feb 2020 · not reviewed since
Ransomware distribution methods vary, so be prepared for all types of attacks
Ransomware is a very lucrative business currently, with many attacks being carried out against high profile companies, industries, government institutions, and also regular users.
The problem is highly complicated by the fact that ransoms are paid to criminals - these payments only fuels the illegal business. However, in some cases, enterprise entities and individuals simply have no other choice.
The best solution would be not being infected in the first place, and for that, adequate security measures are required.
As mentioned previously, hackers may employ a single or multiple attack vectors (for example, Mool, Nppp, and other Djvu variants are being spread across the world with the help of software cracks exclusively, and this technique works extremely well, infecting hundreds daily), so it is important to ensure that comprehensive precautionary measures are applied:
- Do not let spam email attachment run a macro function ("Allow content") or click on links inside;
- Update Windows and the installed programs as soon as possible to avoid software vulnerabilities from being exploited to infect malware automatically;
- Protect all your accounts with security passwords and use two-factor authentication where possible;
- Never download software cracks or pirated program installers from torrent and similar sites;
- Install anti-malware software that would use advanced protection measures, such as machine-learning technology;
- Backup your most important files regularly.
The EncoderCSL ransomware note
Your files has been safely encrypted
Please open READ_ME file on your desktop for decryption
Don't try to decrypt files yourself! It can be damage your files forever!
User ID:
Machine ID:
How to remove EncoderCSL 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 EncoderCSL 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 EncoderCSL 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
.lockedand the instructions are inREAD.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 EncoderCSL 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 EncoderCSL 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 EncoderCSL 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.
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 Feb 2020 · not reviewed since
You should remove EncoderCSL ransomware after you backup the locked data
The immediate EncoderCSL ransomware removal might result in data compromise, so it is important not to do this immediately.
As evident, the malware should be eliminated from the computer as soon as possible, as the infection may render it vulnerable to other cyber attacks.
Therefore, before you remove EncoderCSL ransomware virus from your computer, backup the encrypted files. If you do not care about the text files you have, you can skip this step and simply terminate the malware with the help of powerful anti-malware. Note that, in some cases, you will have to access Safe Mode with networking to prevent the EncoderCSL virus from tampering with your security tool.
Once you are sure that your system is clean, you can employ data recovery methods we provide below, although note that chances of these techniques being successful are very slim. Nevertheless, malware developers, including those behind EncoderCSL, might make mistakes that would allow security experts to create a free decryption tool. Considering how low the distribution of this malware is, the action is highly unlikely, unfortunately.
[GI=method-1]If your anti-virus cannot function in normal mode, access Safe Mode as explained below:
[GI=method-2]System Restore can also be used for EncoderCSL ransomware removal:
While data recovery software is not designed to restore files that were encrypted by ransomware, they might be successful in retrieving at least some of the file copies from the hard drive.
Try out Windows Previous Versions feature
This method will only work if you had System Restore enabled before the infection occurred.
ShadowExplorer might save you from data loss
In case Shadow Volume Copies were preserved, ShadowExplorer should be able to recover all your files automatically.
No decryption tool is currently available
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 EncoderCSL 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 .locked 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 EncoderCSL ransomware
Are ransomware recovery services legitimate?
Some are, but read the offer carefully. Genuine data-recovery firms recover deleted originals from disks or rebuild damaged files, and they say so. Others promise to "decrypt any ransomware" for a fixed price, which is impossible without the key; they quietly pay the attackers and keep a margin, sometimes without telling the victim.
Be especially careful with services that contact you after you post about the attack online. Ask for references, a written method and a no-result-no-fee clause, and check the free tools on No More Ransom first.
How do I open .locked files?
You cannot open them by renaming or by choosing another program. The .locked ending shows that EncoderCSL 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 EncoderCSL ransomware. Store the encrypted files on an external disk until then.
Is there a free EncoderCSL ransomware decryptor?
We last checked on 6 October 2026, and for EncoderCSL 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 "EncoderCSL 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.
Should I pay the ransom?
We advise against it, and so do the FBI, Europol and national cyber agencies. Payment does not guarantee a working tool: some attackers never reply, some tools damage files, and some variants have no decryptor at all. Paying also funds further attacks and can make you a target again.
Before considering payment, try every recovery option in this guide and report the attack. Companies must involve their legal adviser and insurer, because payments to sanctioned groups can be illegal. If files are truly irreplaceable, store the encrypted copies and wait; decryptors sometimes appear later.
How did EncoderCSL ransomware get on my computer?
The way EncoderCSL 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 .locked 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 EncoderCSL ransomware steal my files or passwords?
We do not know yet. Nothing published so far shows data theft by EncoderCSL ransomware, but the only confirmed sign is files that end in .locked 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 EncoderCSL 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 .locked from the file names?
You can try it on a copy, but for real ransomware it will not help. The .locked 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.
Should I open READ.txt?
Reading it is fine if you open it in Notepad. A plain text READ.txt cannot harm the PC. Be careful with notes in HTA or HTML format: double-clicking those runs them in a window that can contain scripts, so right-click and choose Open with > Notepad instead.
The note tells you the contact addresses, the claimed amount and the deadline. Do not visit links or write to the addresses from this PC. Use the note to identify the family and check for a free decryptor first.
Will Fortect remove EncoderCSL 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 EncoderCSL 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
- Wikipedia: Advanced Encryption Standard (read October 6, 2026)
- Zondervirus: Zondervirus (read October 6, 2026)
- Virus Total: EncoderCSL.exe (read October 6, 2026)
- Heimdal Security: This Year in Ransomware Payouts (2019 Edition) (read October 6, 2026)
- CISA: StopRansomware (read October 6, 2026)