Koti Virus ☣ [.KOTI File] — How to Remove Ransomware + Recover PC

Written by Brendan Smith

KOTI Virus

Koti is a DJVU family of ransomware-type infections1. The virus encrypts important personal files (video, photos, documents). The infected files can be tracked by specific “.koti” extension. So, you can’t use them at all.
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In this article I will try to help you remove Koti virus for free. Also I will assist you in decoding your encrypted files.

What is “Koti”?

Koti can be correctly identify as a ransomware infection.
Ransomware is a kind of virus that encrypted your documents and then forces you to pay to restore them. DJVU (aka STOP) ransomware family was first revealed and analyzed by virus analyst Michael Gillespie2.

Koti is similar to other ransomware like: Mzlq, Sqpc, Mpal. It encrypted all popular file types. Hence, users cannot open the your documents or photos. Koti adds its own “.koti” extension into all files. For example, the file “video.avi”, will be changed into “video.avi.koti”. As soon as the encryption is successfully accomplished, Koti creates a special file “_readme.txt” and puts it into all folders that contain the modified files.

Here is a short details for the Koti :
Ransomware family3DJVU/STOP4 ransomware
Ransomware note_readme.txt
RansomFrom $490 to $980 (in Bitcoins)
Contacthelpmanager@mail.ch, restoremanager@firemail.cc
DetectionTrojan-Ransom.Win32.Blocker.ivhl, PWS:Win32/Prast!rfn, Trojan:Win32/Danabot.KM!MTB
SymptomsMost of your files (photos, videos, documents) have a .koti extension and you can’t open it
Fix ToolSee If Your System Has Been Affected by .koti file virus

This text asking payment is for restore files via decryption key:

Koti infection message

The scary alert demanding from users to pay the ransom to decrypt the compromised data contains these frustrating warnings

The cryptography algorithm used by Koti is AES-256. So, if your documents got encrypted with a specific decryption key, which is totally distinct and there are no other copies. The sad reality is that it is impossible to recover the information without the unique key available.

In case if Koti worked in online mode, it is impossible for you to gain access to the AES-256 key. It is stored on a remote server owned by the criminals who promote the Koti infection.

In some cases Koti ransomware uses an offline key for encryption. We have no information about the conditions when ransomware uses the offline key. But, nonetheless, you can check if your files were been encrypted with online or offline key. Find PersonalID file in SystemID folder on the C disk, and check the file for an entry that ends on “t1”. If you find such entry – Koti ransomware used the offline key.

The difference between the offline and online keys is in decryption ease. There is a limited amount of offline keys created for each ransomware. So, there is a chance to meet several Koti ransomware attack cases which were using the same key to encrypt the files. And, as mentioned, for every case of Koti attack with the online key usage the unique key will be created.

For receiving decryption key the payment should be $980. To obtain the payment details, the victims are encouraged by the message to contact the frauds by email (helpmanager@mail.ch), or via Telegram.

Do not pay for Koti!

Please, try to use the available backups, or Decrypter tool

_readme.txt file also indicates that the computer owners must get in touch with the Koti representatives during 72 hours starting from the moment of files where encrypted. On the condition of getting in touch within 72 hours, users will be granted a 50% rebate. Thus the ransom amount will be minimized down to $490). However, stay away from paying the ransom!

I certainly advise that you do not contact these crooks and do not pay. The one of the most real working solution to recover the lost data – just using the available backups, or use Decrypter tool.

The peculiarity of all such viruses apply a similar set of actions for generating the unique decryption key to recover the ciphered data.

Thus, unless the ransomware is still under the stage of development or possesses with some hard-to-track flaws, manually recovering the ciphered data is a thing you can’t perform. The only solution to prevent the loss of your valuable data is to regularly make backups of your crucial files.

Backups are not a panacea for Koti ransomware. It can easily counteract all your attempts to restore data via backups. The most often case for Koti virus is backup contamination. It can both encrypt backup files and inject own .exe file, so after the backup usage your files will be encrypted, again.

Sometimes, Koti ransomware uses much more rough methods, depending on it’s “version”. It can disable an access to your backups or even delete them. However, such actions are usually done with the backups created with built-in Windows tools. Hence, to avoid such troubles, use any other backup creation tools.

There is a chance that some of your files are avaliable after encryption. Koti ransomware has a significant troubles with large files encryption. You can try to remove the .koti extension from your files which are bigger then 1 GB, and then launch it in usual way.

The same action can be done with MP3, MP4 and AVI files. Because of their relatively big size only the first 150 KBs are encrypted. Hence, you can try to open such files with WinAmp, for example. The only problem is that the first 3-5 seconds of the song/video will be missing – this part was been encrypted.

Another method that is used by Koti ransomware is the registry editing. It adds it’s .exe file to the RunOnce key. This key is responsible for launching the programs you’ve added to the Start-up. Hence, after such manipulation ransomware is able to launch simultaneously with Windows, so you cannot stop it with reboot or shutdown.

Note that even if you do maintain such backups regularly, they ought to be put into a specific location without loitering, not being connected to your main workstation.

For instance, the backup may be kept on the USB flash drive or some alternative external hard drive storage. Optionally, you may refer to the help of online (cloud) information storage.

But USB-drives can also been attacked. Koti ransomware can encrypt the files which are stored on the external drive, or even inject own .exe file in this USB. Hence, your USB-drive becomes a ransomware carrier, which is able to infect any PC it is plugged in.

Needless to mention, when you maintain your backup data on your common device, it may be similarly ciphered as well as other data.

For this reason, locating the backup on your main device is surely not a good idea.

How I was infected?

Koti has a various methods to built into your system. But it doesn’t really matter what concrete method had place in your case.

Koti virus attack

Koti attack following a successful phishing attempt.

Nevertheless, these are the common leaks through which it may be injected into your PC:

  • hidden installation along with other apps, especially the utilities that work as freeware or shareware;
  • dubious link in spam emails leading to the Koti installer
  • online free hosting resources;
  • using illegal peer-to-peer (P2P) resources for downloading pirated software.

There were cases when the Koti virus was disguised as some legitimate tool, for example, in the messages demanding to initiate some unwanted software or browser updates. This is typically the way how some online frauds aim to force you into installing the Koti ransomware manually, by actually making you directly participate in this process.

Surely, the bogus update alert will not indicate that you are going to actually inject the Koti ransomware. This installation will be concealed under some alert mentioning that allegedly you should update Adobe Flash Player or some other dubious program whatsoever.

All STOP/Djvu ransomware has a common feature – their distribution model. Koti ransomware, as a part of STOP/Djvu family, is also distributed in a such way – as a part of the malware bundle. This bundle can contain literally any malware, from “simple” browser hijackers and adware to backdoors and trojans. Hence, if you got a “non-critical” (as you think) malware, that’s a reason to perform a full scan of you PC, because something more serious may be inside.

UPD 25.05.2020. We got a lot of compliances about the Koti ransomware distribution via e-mail spamming. Such a letter is usually sent from unknown and strange-looking address and contains an offer to try a new add-on for your Chrome or Mozilla. An attached file is heavily promoted to open, and, of course, you will get a ransomware and a pack of different malware instead of the offered add-on.

UPD 02.06.2020. Another distribution wave is detected. This time, there are a lot of Koti ransomware cases reported by users who downloaded music through torrent-trackers. The majority of cases were detected on Gnutella, one of popular European torrent-trackers.

Of course, the cracked apps represent the damage too. Using P2P is both illegal and may result in the injection of serious malware, including the Koti ransomware.

According to the reports we got, a lot of Koti ransomware copies was been distributed via e-mail spamming. Users told us about the letters from unknown e-mails, which contained an offering “to try a completely new online game”. The e-mail also contained a downloading link, but instead of the game you’ll get a ransomware.

To sum up, what can you do to avoid the injection of the Koti ransomware into your device? Even though there is no 100% guarantee to prevent your PC from getting damaged, there are certain tips I want to give you to prevent the Koti penetration. You must be cautious while installing free software today.

Be very careful with an intrusive advertiserments you can see in Internet. They can offer you to update your browser (even if it is up to date), or say that your PC is full of viruses. But, anyway, the link they contain follows to the dubious site, where the downloading is started without your approval. The file you were downloaded from such sites usually contains a malware and/or Koti ransomware.

The typical “satellites” for Koti ransomware are Wup Trojan and AzorULT Trojan. The first one is a trojan-miner, which uses your PC hardware to mine cryptocurrencies; the second is a trojan-stealer, that is targeted on your personal data, passwords, credit cards data and so on.

Make sure you always read what the installers offer in addition to the main free program. Stay away from opening dubious email attachments. Do not open files from the unknown addressees. Of course, your current security program must always be updated.

The malware does not speak openly about itself. It will not be mentioned in the list of your available programs. However, it will be masked under some malicious process running regularly in the background, starting from the moment when you launch your PC.

The message by the Koti ransomware states the following frustrating information:


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:


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:


Reserve e-mail address to contact us:


Your personal ID:

The image below gives a clear vision of how the files with “.koti” extension look like:

Koti Virus - encrypted .koti files

Example of encrypted .koti files

How to remove Koti virus?

In addition to encode a victim’s files, the Koti infection has also started to install the Azorult Spyware on system to steal account credentials, cryptocurrency wallets, desktop files, and more.
Reasons why I would recommend GridinSoft5

The is an excellent way to deal with recognizing and removing threats – using Gridinsoft Anti-Malware. This program will scan your PC, find and neutralize all suspicious processes6.

Download Removal Tool.

You can download GridinSoft Anti-Malware by clicking the button below:

Run the setup file.

When setup file has finished downloading, double-click on the setup-antimalware-fix.exe file to install GridinSoft Anti-Malware on your computer.

Run Setup.exe

An User Account Control asking you about to allow GridinSoft Anti-Malware to make changes to your device. So, you should click “Yes” to continue with the installation.

GridinSoft Anti-Malware Setup

Press “Install” button.

GridinSoft Anti-Malware Install

Once installed, Anti-Malware will automatically run.

GridinSoft Anti-Malware Splash-Screen

Wait for the Anti-Malware scan to complete.

GridinSoft Anti-Malware will automatically start scanning your computer for Koti infections and other malicious programs. This process can take a 20-30 minutes, so I suggest you periodically check on the status of the scan process.

GridinSoft Anti-Malware Scanning

Click on “Clean Now”.

When the scan has finished, you will see the list of infections that GridinSoft Anti-Malware has detected. To remove them click on the “Clean Now” button in right corner.

GridinSoft Anti-Malware Scan Result

How to decrypt .koti files?

Restore solution for big “.koti files

Try removing .koti extension on a few BIG files and opening them. Either the Koti ransomware read and did not encrypt the file, or it bugged and did not add the filemarker. If your files are very large (2GB+), the latter is most likely. Please, let me know in comments if that will work for you.

The newest extensions released around the end of August 2019 after the criminals made changes. This includes Qewe, Lezp, Lalo, etc.

As a result of the changes made by the criminals, STOPDecrypter is no longer supported. It has been removed and replaced with the Emsisoft Decryptor for STOP Djvu Ransomware developed by Emsisoft and Michael Gillespie.

You can download free decryption tool here: Decryptor for STOP Djvu.

Download and run decryption tool.

Start downloading the decryption tool.

Make sure to launch the decryption utility as an administrator. You need to agree with the license terms that will come up. For this purpose, click on the “Yes” button:

Emsisoft Decryptor - license terms

As soon as you accept the license terms, the main decryptor user interface comes up:

Emsisoft Decryptor - user interface

Select folders for decryption.

Based on the default settings, the decryptor will automatically populate the available locations in order to decrypt the currently available drives (the connected ones), including the network drives. Extra (optional) locations can be selected with the help of the “Add” button.

Decryptors normally suggest several options considering the specific malware family. The current possible options are presented in the Options tab and can be activated or deactivated there. You may locate a detailed list of the currently active Options below.

Click on the “Decrypt” button.

As soon as yo add all the desired locations for decryption into the list, click on the “Decrypt” button in order to initiate the decryption procedure.

Note that the main screen may turn you to a status view, letting you know of the active process and the decryption statistics of your data:

Emsisoft Decryptor - the decryption statistics

The decryptor will notify you as soon as the decryption procedure is completed. If you need the report for your personal papers, you can save it by choosing the “Save log” button. Note that it is also possible to copy it directly to your clipboard and to paste it into emails or forum messages if you need to do so.

Frequently Asked Questions

How can I open “.koti” files?

No way. These files are encrypted by Koti ransomware. The contents of .koti files are not available until they are decrypted.

koti files contain important information. How can I decrypt them urgently?

If your data remained in the .koti files are very valuable, then most likely you made a backup copy.
If not, then you can try to restore them through the system function – Restore Point.
All other methods will require patience.

You have advised using GridinSoft Anti-Malware to remove Koti. Does this mean that the program will delete my encrypted files?

Of course not. Your encrypted files do not pose a threat to the computer. What happened has already happened.

You need GridinSoft Anti-Malware to remove active system infections. The virus that encrypted your files is most likely still active and periodically
runs a test for the ability to encrypt even more files. Also, these viruses install keyloggers and backdoors for further malicious actions
(for example, theft of passwords, credit cards) often.

Decrytor did not decrypt all my files, or not all of them were decrypted. What should I do?

Have patience. You are infected with the new version of Koti ransomware, and decryption keys have not yet been released. Follow the news on our website.
We will keep you posted on when new Koti keys or new decryption programs appear.

What can I do right now?

The Koti ransomware encrypts only the first 150KB of files. So MP3 files are rather large, some media players (Winamp for example) may be able to play the files, but – the first 3-5 seconds (the encrypted portion) will be missing.

You can try to find a copy of an original file that was encrypted:

  • Files you downloaded from the Internet that were encrypted and you can download again to get the original.
  • Pictures that you shared with family and friends that they can just send back to you.
  • Photos that you uploaded on social media or cloud services like Carbonite, OneDrive, iDrive, Google Drive, etc)
  • Attachments in emails you sent or received and saved.
  • Files on an older computer, flash drive, external drive, camera memory card, or iPhone where you transferred data to the infected computer.

If your computer is infected with ransomware, I recommend that you contact the following government fraud and scam sites to report this attack:

Video Guide

It’s my favorite video tutorial: How to use GridinSoft Anti-Malware and Emsisoft Decryptor for fix ransomware infections.

If the guide doesn’t help you to remove Koti infection, please download the GridinSoft Anti-Malware that I recommended. Also, you can always ask me in the comments for getting help.

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Brendan Smith
How to remove KOTI virus and restore PC?

Name: KOTI Virus

Description: Koti is a DJVU family of ransomware-type infections. The virus encrypts important personal files (video, photos, documents). The infected files can be tracked by a specific “.koti” extension. So, you can’t use them at all.

Operating System: Windows

Application Category: Malware

User Review
4.55 (102 votes)
Comments Rating 0 (0 reviews)


  1. Ransomware-type infection: https://en.wikipedia.org/wiki/Ransomware
  2. Twitter: https://twitter.com/demonslay335
  3. My files are encrypted by ransomware, what should I do now?
  4. About DJVU (STOP) Ransomware.
  5. GridinSoft Anti-Malware Review from HowToFix site: https://howtofix.guide/gridinsoft-anti-malware/
  6. More information about GridinSoft products: https://gridinsoft.com/comparison

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About the author

Brendan Smith

I'm Brendan Smith, a passionate journalist, researcher, and web content developer. With a keen interest in computer technology and security, I specialize in delivering high-quality content that educates and empowers readers in navigating the digital landscape.

With a focus on computer technology and security, I am committed to sharing my knowledge and insights to help individuals and organizations protect themselves in the digital age. My expertise in cybersecurity principles, data privacy, and best practices allows me to provide practical tips and advice that readers can implement to enhance their online security.


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