Koti Ransomware - How to remove

Koti is new Djvu-type ransomware, following Mzlq, Sqpc, and others. When Koti infects a computer, it corrupts files and adds a new extension, “.koti”, to their names. It is most dangerous to those who didn’t make backups for their data. Removing Koti can be done with an antivirus program, but fixing the files that Koti encrypted is more complicated – and not always possible.

In short about Koti:

Type of threat	Ransomware, spyware.
How Koti affects PCs	It renames and encrypts various files, corrupting them, creates ransom notes, blocks some websites, disables the antivirus and the task manager, installs a spyware trojan.
How to restore your files	Restore from a backup, repair the individual files, try the free decryptor, archive the encrypted files and wait for a possible solution.
How to remove Koti	Unblock security sites and reinstall your antivirus program (Spyhunter, others), remove malware, change online passwords.

How Koti attacks PCs

Koti is more than just ransomware:

• it encrypts user files or portions of files,
• blocks various websites by editing the hosts file,
• disables the task manager,
• tries to break the local antivirus program by deleting its files,
• installs a password-stealing trojan.

To begin the encryption, Koti might show a fake Windows Update screen. Allowing it to run begins Koti’s encryption. When the Koti ransomware encrypts files, it also changes their names by adding “.koti” as a second extension. For example, a picture encrypted by Koti might be renamed from “picture.jpg” to “picture.jpg.koti”. The same goes for other files: documents, presentations, PDFs, video and audio recordings, etc.

Koti encrypts lots of files very quickly. One of the reasons for this is that it only encrypts portions of the bigger files. However, it’s enough to break those files. Repairing is possible in some cases, but you need to throw out the encrypted portion. And the smaller files might be totally irreparable.

While it’s there, Koti also disables task manager and blocks some websites that are related to cybersecurity.

In addition, Koti installs the password stealer Azorult. Azorult can download and install adware. It can also steal small files, take screenshots, and read email contacts and passwords that are saved in your online apps (such as the browser and the email app). Criminals might try to use your stolen credentials to hack your accounts.

Finally, Koti creates a bunch of files called _readme.txt and puts them in various folders. These are the ransom notes in which the criminals give their contact information ([email protected], [email protected]) and ask for $490 or $980 in exchange for the decryption key. The decryption key is the code that can be used to reverse the encryption done by Koti and fix your files. Each key is unique to each individual victim and there is no way to guess or brute-force the keys.

How to fix the damage

So, the Koti ransomware seems pretty devastating. Luckily, it’s not hopeless.

You can restore the use of task manager and unblock the security sites that Koti blocked (instructions below). After you remove Koti and Azorult, you will need to change your passwords.

As for repairing the files that Koti broke, there are a few possibilities. That is, if you don’t have a backup of your files. If you do have a backup, you only need to remove Koti and other malware and you can replace the encrypted files with the files from your backup.

There is a free decryptor (Emsisoft.com). The problem is that it does not work without the correct decryption key. But if your version of Koti malfunctioned and ran in offline mode (for example, if your computer didn’t have internet connection while Koti was wrecking your files), then it couldn’t have downloaded a unique encryption key and would have needed to use the non-unique offline key. In this case, if someone else gets their offline key, it’ll work on your files, too. Scan your files with Emsisoft’s decryptor to see if this applies to you.

To restore your files without decrypting them, look into repairing corrupted files. The bigger your files, the more data Koti left untouched. And encrypted data can be treated as corrupted data. This requires some dedication and a bit of technical knowledge, but here’s a blog post that deals specifically with images corrupted by ransomware that is related to Koti: Disktuna.com.

There’s a tiny chance that the criminals will eventually be caught and everyone’s decryption keys will be released, or that the criminals will retire and release all the keys themselves. As small as those chances are, you can archive the Koti-encrypted files and wait for such a day. The encrypted files are not dangerous and they won’t harm the devices on which they’re stored.

How to remove Koti ransomware

As for removing Koti, you need to restore the task manager and unblock websites first. Then, use anti-malware programs (such as Spyhunter) to remove malicious programs and files.

Koti spreads with pirated files, mostly. There might be some files in your Downloads folder that need to be deleted. In addition, be very careful where you download programs and files from so that you don’t download Koti or another ransomware again.

Change your passwords and keep an eye on your online accounts, your credit card, your crypt wallet, etc. If there was spyware downloaded with Koti, then it is extremely important to make sure that your money is safe.

Important -- edit the hosts file to unblock security websites

TL DR : The hosts file is edited to block security sites Before the virus can be removed, it's necessary to fix the hosts file (the file which controls which addresses connect to which IPs). That is the reason the majority of security websites is inaccessible when infected with this particular parasite. This infection edits this file to stop certain websites, including anti-malware download sites, from being accessed from the infected computer, making browsers return the "This site can't be reached" error. Luckily, it's trivial to fix the file and remove the edits that were made to it.

Find and edit the hosts file

The hosts file can be found on C:/Windows/System32/Drivers/etc/hosts. If you don't see it, change the settings to see hidden files.

1. In the Start Menu, search for Control Panel.
2. In the Control Panel, find Appearance and Personalization.
3. Select Folder Options.
4. Open the View tab.
5. Open Advanced settings.
6. Select "Show hidden files...".
7. Select OK.

Open this file with administrator privileges.

1. Open the Start Menu and enter "notepad".
2. When Notepad shows up in the result, right-click on it.
3. In the menu, choose "Run as administrator"
4. File->Open and browse for the hosts file.

The hosts file should look like this: Delete additional lines that they connect various domain names to the wrong IP address. Save the file.

Download and run the antivirus program

After that, download antivirus programs and use them to remove the ransomware, the trojan, and other malware. Spyhunter (https://www.2-viruses.com/reviews/spyhunter/dwnld/).

Automatic Malware removal tools

How to recover Koti Ransomware encrypted files and remove the virus

Step 1. Restore system into last known good state using system restore

1. Reboot your computer to Safe Mode with Command Prompt:

for Windows 7 / Vista/ XP

• Start → Shutdown → Restart → OK.
• Press F8 key repeatedly until Advanced Boot Options window appears.
• Choose Safe Mode with Command Prompt.

for Windows 8 / 10

• Press Power at Windows login screen. Then press and hold Shift key and click Restart.
• Choose Troubleshoot → Advanced Options → Startup Settings and click Restart.
• When it loads, select Enable Safe Mode with Command Prompt from the list of Startup Settings.

 

2.Restore System files and settings.

• When Command Prompt mode loads, enter cd restore and press Enter.
• Then enter rstrui.exe and press Enter again.
• Click “Next” in the windows that appeared.
• Select one of the Restore Points that are available before Koti Ransomware has infiltrated to your system and then click “Next”.
• To start System restore click “Yes”.

 

Step 2. Complete removal of Koti Ransomware

After restoring your system, it is recommended to scan your computer with an anti-malware program, like Spyhunter and remove all malicious files related to Koti Ransomware. You can check other tools here.  

Step 3. Restore Koti Ransomware affected files using Shadow Volume Copies

If you do not use System Restore option on your operating system, there is a chance to use shadow copy snapshots. They store copies of your files that point of time when the system restore snapshot was created. Usually Koti Ransomware tries to delete all possible Shadow Volume Copies, so this methods may not work on all computers. However, it may fail to do so. Shadow Volume Copies are only available with Windows XP Service Pack 2, Windows Vista, Windows 7, and Windows 8. There are two ways to retrieve your files via Shadow Volume Copy. You can do it using native Windows Previous Versions or via Shadow Explorer. a) Native Windows Previous Versions Right-click on an encrypted file and select Properties → Previous versions tab. Now you will see all available copies of that particular file and the time when it was stored in a Shadow Volume Copy. Choose the version of the file you want to retrieve and click Copy if you want to save it to some directory of your own, or Restore if you want to replace existing, encrypted file. If you want to see the content of file first, just click Open.

b) Shadow Explorer It is a program that can be found online for free. You can download either a full or a portable version of Shadow Explorer. Open the program. On the left top corner select the drive where the file you are looking for is a stored. You will see all folders on that drive. To retrieve a whole folder, right-click on it and select “Export”. Then choose where you want it to be stored.

Step 4. Use Data Recovery programs to recover Koti Ransomware encrypted files

There are several data recovery programs that might recover encrypted files as well. This does not work in all cases but you can try this:

• We suggest using another PC and connect the infected hard drive as slave. It is still possible to do this on infected PC though.
• Download a data recovery program.
• Install and scan for recently deleted files.

Note: In many cases it is impossible to restore data files affected by modern ransomware. Thus I recommend using decent cloud backup software as precaution. We recommend checking out Carbonite, BackBlaze, CrashPlan or Mozy Home.