How to remove Koti ransomware from your operating system?

Also Known As: Koti virus
Distribution: Low
Damage level: Severe

Koti ransomware removal instructions

What is Koti?

Koti is a piece of malicious software, which is part of the Djvu ransomware family. It is designed to encrypt the files of infected systems in order to make ransom demands. As this ransomware encrypts, all of the affected files are appended with the ".koti" extension. For example, a file originally titled something like "1.jpg" would appear as "1.jpg.koti" - after encryption. Following the end of this process, a text file - "_readme.txt" - is created dropped into every compromised folder.

The ransom note in "_readme.txt" reassures victims that it is possible to recover their data. Users are informed that their files have been encrypted with strongest encryption and unique key. The sole method of restoring them is by purchasing decryption keys and software from the cyber criminals behind Koti. Before paying, victims can test decryption by sending one encrypted non-valuable file via email. The decryption of said file will serve as proof that recovery is viable. The size of the ransom is listed as 980 USD. If contact with the criminals is established within the first 72 hours, a 50% percent discount will be available - thereby, halving the price to 490 USD. Should no response arrive within 6 hours, users are instructed to inspect their "Spam/Junk" email folders, as the reply may have gotten sent to this part of their inbox. Unfortunately, in most cases of ransomware infections, without involving the cyber criminals responsible - decryption is impossible. It might be, if the malware has significant flaws and/or is still in development. Regardless, it is expressly advised against meeting the ransom demands. There no guarantees that the criminals will hold true to their word, and often - they do not. Therefore, despite paying - it is common for victims not to receive the necessary tools to decrypt their data. To prevent Koti ransomware from encrypting more files - it must be removed from the operating system. However, removal will not restore already compromised data. The only solution is recovering the files from a backup, if one was made before the infection and was stored in a different location.

Screenshot of a message encouraging users to pay a ransom to decrypt their compromised data:

Koti decrypt instructions (_readme.txt)

Ransomware operates by encrypting data and demanding payment for the decryption tools/software. ZoNiSoNaLQolkuzNbVcG and Zeronine are a few examples of malicious programs within this category. These programs/infections are not identical, the main differences between them are: the cryptographic algorithm they use (symmetric or asymmetric) and the ransom size. The demanded sums typically range from three to four digits in USD. Digital currencies (primarily, cryptocurrencies) are used for the payments, due to transactions of them being difficult/impossible to trace. To protect data safety, it is recommended to keep backups in remote servers and/or unplugged storage devices (ideally, in multiple separate locations).

How did ransomware infect my computer?

The most common methods of ransomware and other malware distribution include spam campaigns, trojans, illegal activation tools ("cracks"), illegitimate updates and untrustworthy download sources. The term "spam campaign" refers to a large scale operation, during which deceptive emails are sent by the thousand. These letters are usually presented as "official", "urgent", "important" and similar. They have infectious files attached or contain download links of them. Virulent files can be in various formats (e.g. archives, executables, Microsoft Office and PDF files, JavaScript, etc.); when they are executed, run or otherwise opened - the infection process is triggered (i.e. malware download/installation is initiated). Trojans are malicious programs, some types of which can cause chain infections. Rather than activate licensed software, "cracking" tools can download/install malware. Fake updaters infect systems by exploiting weaknesses of outdated software and/or by simply installing malicious programs instead of the promised updates. Untrustworthy download channels, like: unofficial and free file-hosting (freeware) sites, Peer-to-Peer sharing networks (BitTorrent, eMule, Gnutella, etc.) and other third party downloaders - can offer malware, disguised as or packed together with ordinary content.

Threat Summary:
Name Koti virus
Threat Type Ransomware, Crypto Virus, Files locker
Encrypted Files Extension .koti
Ransom Demanding Message _readme.txt
Ransom Amount $980 or $490
Cyber Criminal Contact helpmanager@mail.ch and restoremanager@firemail.cc
Detection Names Avast (Win32:CoinminerX-gen [Trj]), BitDefender (Trojan.GenericKDZ.67221), ESET-NOD32 (A Variant Of Win32/Kryptik.HDKV), Kaspersky (Hoax.Win32.ArchSMS.cqrgr), Full List Of Detections (VirusTotal)
Rogue Process Name 5.exe (process name may vary)
Symptoms Cannot open files stored on your computer, previously functional files now have a different extension (for example, my.docx.locked). A ransom demand message is displayed on your desktop. Cyber criminals demand payment of a ransom (usually in bitcoins) to unlock your files.
Additional Information This malware is designed to show a fake Windows Update window and modify the Windows "hosts" file to prevent users from accessing cyber security websites (more information below).
Distribution methods Infected email attachments (macros), torrent websites, malicious ads, unofficial activation and updating tools.
Damage All files are encrypted and cannot be opened without paying a ransom. Additional password-stealing trojans and malware infections can be installed together with a ransomware infection.
Malware Removal (Windows)

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How to protect yourself from ransomware infections?

To avoid infectious content proliferated via spam mail, it is advised not to open suspicious and/or irrelevant emails - especially and attachments or links found in them. Additionally, it is important to only use official and verified download sources. It is strongly recommended to activate and update programs with tools/functions, provided by legitimate developers. Illegal activation tools ("cracks") and third party updaters should not be used, as they are often employed to distribute malware. To ensure device integrity and user safety, it is paramount to have a dependable anti-virus/anti-spyware suite installed. This software must be kept up-to-date, used to run regular system scans and to remove detected threats. If your computer is already infected with Koti, we recommend running a scan with Malwarebytes for Windows to automatically eliminate this ransomware.

Text presented in Koti ransomware's text file ("_readme.txt"):

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.cc

 

Your personal ID:
-

Screenshot of files encrypted by Koti (".koti" extension):

Files encrypted by Koti ransomware (.koti extension)

Screenshot of Koti ransomware's process on Windows Task Manager ("5.exe"):

Koti ransomware process on task manager (5.exe)

Screenshot of fake Windows update pop-up displayed during the encryption:

Fake Windows pop-up displayed by Koti during the encryption

IMPORTANT NOTE! - As well as encrypting data, ransomware-type infections from the Djvu malware family also add a number of entries to the Windows "hosts" file. The entries contain URLs of various websites, most of which are related to malware removal. This is done to prevent users from accessing malware security websites and seeking help. Our website (PCrisk.com) is also on the list. Removing these entries, however, is simple - you can find detailed instructions in this article (note that, although the steps are shown in the Windows 10 environment, the process is virtually identical on all versions of the Microsoft Windows operating system).

Screenshot of websites added to Windows hosts file:

Tro Ransomware adding websites to Windows Hosts file

There are currently two versions of Djvu ransomware infections: old and new. The old versions were designed to encrypt data by using a hard-coded "offline key" whenever the infected machine had no internet connection or the server was timing out/not responding. Therefore, some victims were able to decrypt data using a tool developed by cyber security researcher, Michael Gillespie, however, since the encryption mechanism has been slightly changed (hence the new version, released in August, 2019), the decrypter no longer works and it is not supported anymore. If your data has been encrypted by an older version, you might be able to restore it with the another tool developed by Emsisoft and Michael Gillespie. It supports a total of 148 Djvu's variants and you can find more information, as well as download link and decryption instructions in Emsisoft's official page.

Screenshot of Djvu decryption tool by Emsisoft and Michael Gillespie:

Djvu ransomware decrypter by Michael Gillespie and Emsisoft

Additionally, Emsisoft is now providing a service that allows to decrypt data (again, only if it was encrypted by Djvu variants released before August, 2019) for those victims who have a pair of the same file before and after the encryption. All victims have to do is upload a pair of original and encrypted file to Emsisoft's Djvu decryption page and download the aforementioned decryption tool (the download link will be provided after uploading files). Note that the file processing may take some time so be patient. It is also worth mentioning that the system must have an Internet connection during the entire decryption process, otherwise it will fail.

Screenshot of Emsisoft's Djvu decryption service page:

Djvu ransomware decryption service by Emsisoft

Koti ransomware removal:

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Quick menu:

Isolating the infected device:

Some ransomware-type infections are designed to encrypt files within external storage devices, infect them, and even spread throughout the entire local network. For this reason, it is very important to isolate the infected device (computer) as soon as possible.

Step 1: Disconnect from the internet.

The easiest way to disconnect a computer from the internet is to unplug the Ethernet cable from the motherboard, however, some devices are connected via a wireless network and for some users (especially those who are not particularly tech-savvy), disconnecting cables may seem troublesome. Therefore, you can also disconnect the system manually via Control Panel:

Navigate to the "Control Panel", click the search bar in the upper-right corner of the screen, enter "Network and Sharing Center" and select search result: Disconnecting computer from the Internet (step 1)

Click the "Change adapter settings" option in the upper-left corner of the window: Disconnecting computer from the Internet (step 2)

Right-click on each connection point and select "Disable". Once disabled, the system will no longer be connected to the internet. To re-enable the connection points, simply right-click again and select "Enable". Disconnecting computer from the Internet (step 3)

Step 2: Unplug all storage devices.

As mentioned above, ransomware might encrypt data and infiltrate all storage devices that are connected to the computer. For this reason, all external storage devices (flash drives, portable hard drives, etc.) should be disconnected immediately, however, we strongly advise you to eject each device before disconnecting to prevent data corruption:

Navigate to "My Computer", right-click on each connected device and select "Eject": Ejecting external storage devices

Step 3: Log-out of cloud storage accounts.

Some ransomware-type might be able to hijack software that handles data stored within "the Cloud". Therefore, the data could be corrupted/encrypted. For this reason, you should log-out of all cloud storage accounts within browsers and other related software. You should also consider temporarily uninstalling the cloud-management software until the infection is completely removed.

Identify the ransomware infection:

To properly handle an infection, one must first identify it. Some ransomware infections use ransom-demand messages as an introduction (see the WALDO ransomware text file below).

Identify ransomware-type infection (step 1)

This, however, is rare. In most cases, ransomware infections deliver more direct messages simply stating that data is encrypted and that victims must pay some sort of ransom. Note that ransomware-type infections typically generate messages with different file names (for example, "_readme.txt", "READ-ME.txt", "DECRYPTION_INSTRUCTIONS.txt", "DECRYPT_FILES.html", etc.). Therefore, using the name of a ransom message may seem like a good way to identify the infection. The problem is that most of these names are generic and some infections use the same names, even though the delivered messages are different and the infections themselves are unrelated. Therefore, using the message filename alone can be ineffective and even lead to permanent data loss (for example, by attempting to decrypt data using tools designed for different ransomware infections, users are likely to end up permanently damaging files and decryption will no longer be possible even with the correct tool).

Another way to identify a ransomware infection is to check the file extension, which is appended to each encrypted file. Ransomware infections are often named by the extensions they append (see files encrypted by Qewe ransomware below).

Identify ransomware-type infection (step 2)

This method is only effective, however, when the appended extension is unique - many ransomware infections append a generic extension (for example, ".encrypted", ".enc", ".crypted", ".locked", etc.). In these cases, identifying ransomware by its appended extension becomes impossible.

One of the easiest and quickest ways to identify a ransomware infection is to use the ID Ransomware website. This service supports most existing ransomware infections. Victims simply upload a ransom message and/or one encrypted file (we advise you to upload both if possible).

Identify ransomware-type infection (step 3)

The ransomware will be identified within seconds and you will be provided with various details, such as the name of the malware family to which the infection belongs, whether it is decryptable, and so on.

Example 1 (Qewe [Stop/Djvu] ransomware):

Identify ransomware-type infection (step 4)

Example 2 (.iso [Phobos] ransomware):

Identify ransomware-type infection (step 5)

If your data happens to be encrypted by a ransomware that is not supported by ID Ransomware, you can always try searching the internet by using certain keywords (for example, ransom message title, file extension, provided contact emails, cryptowallet addresses, etc.).

Search for ransomware decryption tools:

Encryption algorithms used by most ransomware-type infections are extremely sophisticated and, if the encryption is performed properly, only the developer is capable of restoring data. This is because decryption requires a specific key, which is generated during the encryption. Restoring data without the key is impossible. In most cases, cyber criminals store keys on a remote server, rather than using the infected machine as a host. Dharma (CrySis), Phobos, and other families of high-end ransomware infections are virtually flawless, and thus restoring data encrypted without the developers' involvement is simply impossible. Despite this, there are dozens of ransomware-type infections that are poorly developed and contain a number of flaws (for example, the use of identical encryption/decryption keys for each victim, keys stored locally, etc.). Therefore, always check for available decryption tools for any ransomware that infiltrates your computer.

Finding the correct decryption tool on the internet can be very frustrating. For this reason, we recommend that you use the No More Ransom Project and this is where identifying the ransomware infection is useful. The No More Ransom Project website contains a "Decryption Tools" section with a search bar. Enter the name of the identified ransomware, and all available decryptors (if there are any) will be listed.

Searching for ransomware decryption tools in nomoreransom.org website

Restore files with data recovery tools:

Depending on the situation (quality of ransomware infection, type of encryption algorithm used, etc.), restoring data with certain third-party tools might be possible. Therefore, we advise you to use EaseUS Data Recovery Wizard Pro. This tool supports over a thousand data types (graphics, video, audio, documents, etc.) and it is very intuitive (little knowledge is necessary to recover data).

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EaseUS Data Recovery Wizard Pro

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Step 1: Perform a scan.

Hover your mouse over the partition you wish to scan and select "Scan". You can also select a specific folder, or click shortcut icons to scan the Desktop or Recycle Bin: Scanning the storage drive with EaseUS Data Recovery Wizard PRO (step 1)

Wait for EaseUS Data Recovery Wizard Pro to complete the scan. The scanning duration depends on the volume of files (both in quantity and size) that you are scanning (for example, several hundreds gigabytes could take over an hour to scan). Therefore, be patient during the scanning process. We also advise against modifying or deleting existing files, since this might interfere with the scan. If you add additional data (for example, downloading files/content) while scanning, this will prolong the process: Scanning the storage drive with EaseUS Data Recovery Wizard PRO (step 2)

Step 2: Recover data.

Once the process is complete, select the folders/files you wish to restore and simply click "Recover". Note that some free space on your storage drive is necessary to restore data. Note also that the trial version of EaseUS Data Recovery Wizard Pro is only capable of scanning drives and listing recoverable files - to restore them, you must purchase a license: Recovering data with EaseUS Data Recovery Wizard Pro

Step 3: Save the scan session (optional).

We recommend that you save the scanning session once you have completed recovery, in case you decide to recover additional files later. Simply click the "Save Scan Session" icon in the upper-right corner of the screen and choose the location for the file to be saved. This will save a lot of time, since you will not need to re-scan the storage drive the next time you wish to restore something. Bear in mind, however, that data removed after the scanning session has finished will not be listed: Saving scan session in EaseUS Data Recovery Wizard Pro

Create data backups:

Proper file management and creating backups is essential for data security. Therefore, always be very careful and think ahead.

Partition management: We recommend that you store your data in multiple partitions and avoid storing important files within the partition that contains the entire operating system. If you fall into a situation whereby you cannot boot the system and are forced to format the disk on which the operating system is installed (in most cases, this is where malware infections hide), you will lose all data stored within that drive. This is the advantage of having multiple partitions: if you have the entire storage device assigned to a single partition, you will be forced to delete everything, however, creating multiple partitions and allocating the data properly allows you to prevent such problems. You can easily format a single partition without affecting the others - therefore, one will be cleaned and the others will remain untouched, and your data will be saved. Managing partitions is quite simple and you can find all necessary information on Microsoft's documentation web page.

Data backups: The most reliable backup method is to use an external storage device and keep it unplugged. Copy your data to an external hard drive, flash (thumb) drive, SSD, HDD, or any other storage device, unplug it and store it in a dry place away from sun and extreme temperatures. This method is, however, quite inefficient, since data backups and updates need to be made regularly. You can also use a cloud service or remote server. Here, an internet connection is required and there is always the chance of a security breach. Therefore, you should consider using an application to create data backups locally.

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EaseUS Todo Backup

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We recommend using the EaseUS Todo Backup application. The "Home" edition of EaseUS Todo Backup is usually more than adequate for regular users, however, the "Business" edition is more suitable for companies and large computer networks. The EaseUS Todo Backup application provides extensive data protection features. You can easily create backups, and encrypt and compress them for enhanced protection and storage saving purposes. It also allows you to set backup schedules, create bootable devices, and restore the system if a crash occurs. You can easily choose where to store the created backup: locally; uploaded to an external drive; FTP; cloud storage, or elsewhere. In summary, EaseUS Todo Backup is an all-in-one tool, which provides all features required to properly backup your data.

Creating a data backup:

The backup process is virtually identical regardless of the item (file, partition, entire system) you wish to backup. Taking the File Backup feature as an example:

Step 1: Choose which item to backup.

Click on the "Menu" icon in the upper-left corner of the screen to reveal the menu and select "File Backup": Creating data backups with EaseUS Todo Backup tool (step 1)

Select the files you want to backup. You can also enter a name and description of the backup that will be created: Creating data backups with EaseUS Todo Backup tool (step 2)

Step 2: Change the default settings.

The EaseUS Todo Backup application provides a variety of additional options that can be added/modified while creating the backup. For example, you can encrypt data (add a password), select the compression rate (how much the backup should be compressed), performance (how many system resources should be allocated), add an email notification (you receive an email once the process is complete) and so on.

To open the options window, click the "Backup options" button in the lower-left corner of the screen: Creating data backups with EaseUS Todo Backup tool (step 3)

Select the settings you want to change and click "Save". You can also reset your changes by clicking "Reset to initial settings": Creating data backups with EaseUS Todo Backup tool (step 4)

Step 3: Select the backup destination.

As mentioned above, EaseUS Todo Backup allows you to choose where backups are saved - locally or externally.

Click the "Browse..." button and select the location you want the backup to be saved: Creating data backups with EaseUS Todo Backup tool (step 5)

Step 4: Safety measures and process completion.

Depending on the location you have chosen, there are a number of measures you should or should not take. If you are uploading to an internet-connected location (for example, Cloud storage, FTP, etc.), be sure to maintain your internet connection, otherwise you will have to start again. The same applies to external storage devices - do not unplug them until the process is complete.

The progress bar displays estimated time remaining until completion. Large backups (hundreds of gigabytes) can take hours to create (depending on storage device speed, internet connection, etc.). Therefore, the application also allows you to optionally choose what the system should do (shut down, sleep or hibernate) once the process has finished: Creating data backups with EaseUS Todo Backup tool (step 6)

The best way to avoid damage from ransomware infections is to maintain regular up-to-date backups.

About the author:

Tomas Meskauskas

Tomas Meskauskas - expert security researcher, professional malware analyst.

I am passionate about computer security and technology. I have an experience of over 10 years working in various companies related to computer technical issue solving and Internet security. I have been working as an author and editor for pcrisk.com since 2010. Follow me on Twitter and LinkedIn to stay informed about the latest online security threats. Contact Tomas Meskauskas.

PCrisk security portal is brought by a company RCS LT. Joined forces of security researchers help educate computer users about the latest online security threats. More information about the company RCS LT.

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Malware activity

Global malware activity level today:

Medium threat activity

Increased attack rate of infections detected within the last 24 hours.

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Koti virus QR code
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