Koti ransomware: what it is and how to remove it
Koti ransomware is the latest version of the infamous Djvu family of crypto-malware. Resurfaced in the middle of May 2020, it takes the 226th position in the list of STOP/Djvu variants and stands in line with .mpal, .sqpc, and .mzlq entries.
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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Koti ransomware: summary
| Distribution | This extortionist is typically distributed via malicious e-mail message attachments, unprotected RDP ports, P2P networks, or pirated software |
|---|---|
| Damage | The ransomware removal does not ensure full recovery of the affected system files. To fix Windows registry entries, boot files, and other core components, use FortectIntego utility. |
| Name | Koti |
| Family | The infamous group of STOP / Djvu ransomware |
| Detection | May 2020. The first ransomware sample has been uploaded into the official Emsisoft's support[1] site; no Microsoft detection name is known for this name |
| Classification | The Koti virus falls for the ransomware or file-encrypting malware group |
| 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
| Version number | This ransomware is currently the latest djvu version, which stands 226th in the list |
|---|---|
| File marker | The viruses uses .koti file extension to mark locked files |
| Encryption model | RSA |
| Other traits | One the payload is launched, the ransomware locks files and drops a ransom note _readme.txt, which contains a detailed guide on how to pay the ransom |
| Payment conditions | Criminals urge victims to pay $490 if the payment is transferred within 72 hours. If the victim delays the payment, the price is doubled and reaches $980. The only currency accepted – Bitcoin. |
| Ransom note | _readme.txt; the text is quoted in full below |
| Contact | helpmanager@mail.ch, restoremanager@firemail.ch |
| Encrypted file extension | .koti |
| Decryptor | No free decryptor is known for this variant; check No More Ransom (nomoreransom.org) for updates |
| 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 | .koti |
| Attacker contacts | helpmanager@mail.ch |
| Free decryptor | No free decryptor is known (checked 7 October 2026) |
| First seen | 18 May 2020 |
| Facts checked | 7 October 2026 |
- File extension:
.koti - Note file:
_readme.txt - Contact:
helpmanager@mail.ch
From our report of May 2020 · not reviewed since
More from our earlier report on Koti
- It is not possible to detect malicious ransomware files manually.
- The detection and removal of the intruder is possible with a professional AV engine.
How Koti ransomware behaves
From our report of May 2020 · not reviewed since
Koti is the 226th Djvu ransomware family member that emerged in the middle of May 2020
Koti ransomware is the latest version of the infamous Djvu family of crypto-malware.
Resurfaced in the middle of May 2020, it takes the 226th position in the list of STOP/Djvu variants and stands in line with .mpal, .sqpc, and .mzlq entries.
Alike its predecessors, Koti ransomware uses RSA encryption model to lock non-system files and uses a standard _readme.txt ransom note. Besides, it is using the .koti file extension to separate encrypted documents, pictures, videos, photos, databases, archives, and other data from the others.
The criminals behind Koti ransomware are using the helpmanager@mail.ch and restoremanager@firemail.ch emails for contacts. Apparently, they are using the same extortion scheme as the victims are demanded to pay the $980 in Bitcoins as a ransom for a decryptor, though promise to double down the price if the payment comes within 72 hours.
Koti ransomware has been expected to manifest in May, since Djvu ransomware is infamous for its regular release of renewed versions. The first sample of this virus has been uploaded into Emsisoft's support forum where the victim presented the _readme.txt file accompanied by a file locked by .koti file extension.
A close investigation proved the evidence of Koti to be rooted from Djvu ransomware family. It uses a similar base for the distribution, infiltration, encryption, and extortion. According to researchers, its payload is typically distributed via obfuscated spam email attachments or pirated software. Besides, it may also be used for spreading the infamous AZORult trojan as a secondary payload.
Upon successful infiltration, the ransomware begins the first phase of the deployment. The malware settles down multiple boot processes, launches PowerShell to delete Shadow Volume Copies, and disables the AV engine to evade immediate removal. Koti ransomware may also corrupt Windows host files and establish firewall access to security-related forums and websites containing guidelines on how to remove the ransomware and recover damaged files.
This cyber infection is not a threat to mess with as it may cost you a permanent file loss. The best solution for its victims is a full Koti ransomware removal using a program like , , or another professional antivirus tool.
This file-encrypting virus can not only encrypt the data on the host machine, but also plant multiple malicious files, compromise the system severely, and download the Azorult trojan as a secondary payload. Consequently, criminals may get access to your personally identifiable information (PII) , including saved passwords, banking information, login details, etc.
The changes that the Koti ransowmare initiates can hardly be overlooked. Initially, it starts running malicious processes within Task Manager, which is why CPU usage may increase significantly. The most obvious sign indicating ransomware infection is the .koti file extension appended to the pictures, archives, Microsoft Office documents, videos, and other non-system files.
As a final point, the virus creates a _readme.txt ransom note on the random system's folders and the desktop. The note contains the detailed instructions on how to contact ransomware developers and how to transfer the ransom. In short, the victims are expected to contact the crooks via the helpmanager@mail.ch and restoremanager@firemail.ch emails and transmit a ransom, which varies from $480 to $980 in Bitcoins.
Indeed, criminals who promote this ransomware virus expects to extort as much money as possible. However, our biggest piece of advice is to remove Koti ransomware in the first place and then try to recover files using third-party software. Do not get scared by claims that you will lose the files permanently by running an AV scan. Criminals use such and similar scare tactics to catch victims on the hook.
After full Koti ransomware removal, you can start thinking about a recovery of the encrypted data. Since Djvu is one of the largest ransomware families on the surface, cybersecurity experts have invested much time to develop a free decryption software.
At the moment, the Dr. Web Rescue Pack is probably the most reliable tool for retrieving files. However, not all Djvu variants can successfully be crashed by this tool. In case of a failure, try alternative data recovery methods listed at the end of this article.
From our report of May 2020 · not reviewed since
Methods that criminals engage for ransomware distribution
Experts from LosVirus.es provided us with their findings on the methods that cybercriminals are typically using to spread ransomware infections.
According to them, the most popular medium to spread malicious payloads is spam. Hackers craft reliable-looking email messages mimicking the style of various companies (DHL, FedEx, White House, Red Cross, etc.) and disguise ransomware under infected "order confirmations" or similar attachments.
Nevertheless, spam email attachments are not the only ransomware transmitters. Crooks often exploit vulnerable Remote Desktop Protocol (RDP) network connections and use brute-force attacks to infect target systems. The TCP port 3389 is one of the most frequently exploited vulnerabilities allowing criminals to easily attack potential victims. P2P networks, illegal or hacked websites, software cracks, keygens, and other online content that can easily be exploited by hackers.
Thus, having an anti-virus program installed is not sufficient to protect the system from malware. A user's consciousness is equally important. First of all, people should start taking care of the backups, at least backup the most important data, such as documents or family photos. Second of all, think twice before downloading illicit software or visiting potentially dangerous domain.
The Koti ransomware note
ATTENTION!
Don't worry, you can return all your files!
All your files like photos, databases, documents and other important are encrypted with strongest encryption and unique key.
The only method of recovering files is to purchase decrypt tool and unique key for you.
This software will decrypt all your encrypted files.
What guarantees you have?
You can send one of your encrypted file from your PC and we decrypt it for free.
But we can decrypt only 1 file for free. File must not contain valuable information.
You can get and look video overview decrypt tool:
hxxps://we.tl/t-EEHXgjySek
Price of private key and decrypt software is $980.
Discount 50% available if you contact us first 72 hours, that's price for you is $490.
Please note that you'll never restore your data without payment.
Check your e-mail "Spam" or "Junk" folder if you don't get answer more than 6 hours.
To get this software you need write on our e-mail:
helpmanager@mail.ch
Reserve e-mail address to contact us:
restoremanager@firemail.ch
Your personal ID:
How to remove Koti 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 Koti 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
Koti 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
_readme.txtand one or two files ending in.kotito 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 Koti, no free decryptor is known (checked 7 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 Koti 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 May 2020 · not reviewed since
Use a professional AV engine to remove Koti ransomware
Koti ransomware removal requires the usage of a powerful antivirus program.
If you've ever dealt with a ransomware-type virus, you should know that manual removal is not possible under any circumstances. File-encrypting viruses are built in a very comprehensive manner as they infiltrate tens of malicious files in diverse system's places to make Windows conform to malicious commands.
That's a necessary precautionary measure to prevent permanent loss of files encrypted by .koti file extension.
For a full Koti removal use , or an alternative AV engine of your preferences. After that, try to recover the data using the recovery solutions provided below.
[GI=method-1]Since the malicious files run by Koti ransomware can block antivirus programs, you may need to reboot the system into Safe Mode to enable the security program.
[GI=method-2]Use these steps to activate System Restore and prevent all malicious activities from continuation
Unfortunately, the official Koti decryptor hasn't yet been developed. Nevertheless, there's a handful of options that you can try to recover data compromised by this malicious virus.
Nevertheless, before launching it, make sure that you have initiated a successful Koti removal.
Try Windows Previous Version feature
If you have had enabled the Windows Previous Version feature on your PC, then try getting your files back using this software.
Recover files from Volume Shadow Copies
It is known that most of Djvu ransomware variants are programmed to remove Volume Shadow Copies. Nevertheless, it's not clear if Koti ransomware virus deletes these copies, so if none of the previous recovery options helped, give Volume Shadow Copies a try.
No official Koti decrypted available
Since Koti is a fresh cyber infection, researchers did not manage to create a decryption software for it. Nevertheless, it's advisable to try a DrWeb Rescue Pack.
Moreover, a member of the ransomware hunters team called DemonSlay355 launched a free STOPdecryptor, which can help people decrypt some of the Djvu variants that have a personal ID number 6se9RaIxXF9m70zWmx7nL3bVRp691w4SNY8UCir0. If such a number has been generated for you by Koti ransomware, you can download a decryptor from here.
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 Koti 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 .koti and no longer open.
Setting it up step by step: 3-2-1 backups on Windows 11 and 10.
Access your website securely from any location
When you work on the domain, site, blog, or different project that requires constant management, content creation, or coding, you may need to connect to the server and content management service more often. The best solution for creating a tighter network could be a dedicated/fixed IP address.
If you make your IP address static and set to your device, you can connect to the CMS from any location and do not create any additional issues for the server or network manager that needs to monitor connections and activities. VPN software providers like can help you with such settings and offer the option to control the online reputation and manage projects easily from any part of the world.
Recover files after data-affecting malware attacks
While much of the data can be accidentally deleted due to various reasons, malware is one of the main culprits that can cause loss of pictures, documents, videos, and other important files.
More serious malware infections lead to significant data loss when your documents, system files, and images get encrypted. In particular, ransomware is is a type of malware that focuses on such functions, so your files become useless without an ability to access them.
Even though there is little to no possibility to recover after file-locking threats, some applications have features for data recovery in the system. In some cases, can also help to recover at least some portion of your data after data-locking virus infection or general cyber infection.
Questions about Koti ransomware
How do I open .koti files?
You cannot open them by renaming or by choosing another program. The .koti ending shows that Koti 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 Koti. Store the encrypted files on an external disk until then.
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 Koti get on my computer?
The way Koti 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 .koti 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 Koti steal my files or passwords?
We do not know yet. Nothing published so far shows data theft by Koti, but the only confirmed sign is files that end in .koti 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 Koti decryptor?
We last checked on 7 October 2026, and for Koti 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 "Koti 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.
Is Koti 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 .koti from the file names?
You can try it on a copy, but for real ransomware it will not help. The .koti 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 _readme.txt?
Reading it is fine if you open it in Notepad. A plain text _readme.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 Koti?
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 Koti, 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
- Emsisoft: KOTI files encryption (read October 7, 2026)
- CSO Online: What is personally identifiable information (PII)? How to protect it under GDPR (read October 7, 2026)
- LosVirus: NOTICIAS SOBRE SEGURIDAD Y VIRUS (read October 7, 2026)
- CISA: StopRansomware (read October 7, 2026)
- No More Ransom (read October 7, 2026)