How to remove Kolz ransomware

Kolz ransomware is a new Djvu virus version that encrypts files and tries to demand money

Kolz ransomware is another dangerous virus that manages to encrypt^[1] most of the useful files and then demands a ransom to be paid for the return. The virus enters the computer system and disrupts important data in various formats: images, documents, videos, archives, and other files. Users see a ransom note file, named as _readme.txt, in each computer folder with locked files and on the desktop. This way, hackers let victims find out what happened to their files and what they have to do to decrypt them. However, the ransomware creators claim that the only option for the victim is to pay a ransom. This shouldn't be considered a solution because criminals focus on getting money, not helping victims.

Users are asking how to repair affected files and clear the infection. We do not recommend contacting these hackers or paying money because criminals cannot be trusted. Even if you pay them, hackers might never give the ransomware decryptor. .Kolz virus can trigger other changes besides the encryption, so you should get rid of the threat as soon as you possibly can. The best option would be to clear the machine properly with an anti-malware tool. Cleaning the system is the first step before the data recovery using your file backups or third-party programs designed for file recovery.

Kolz ransomware belongs to well-known crypto-malware families – STOP/Djvu. It was spotted the first time in December 2016. Malware creators release new versions regularly, several times a month. It is the most successful data-encrypting malware so far and targets regular users.

All malware variants released until August 2019 were decryptable by security researchers because STOPDecrypter was developed and used with offline IDs. Since then hackers have updated their encryption method to make sure that it would be almost impossible for security specialists to find the solution.

Cybercriminals began using RSA cipher instead of a less reliable AES, so the procedure of file locking is more powerful, and affected files can become permanently locked or even damaged. Though paying Kolz virus creators is not the best option.^[2] Ignore the message and demands instead.

If you do not know how Kolz file virus creators deliver their demands, there is the example of their text file with a message:

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-ccUfUrQOhF
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@airmail.cc

Your personal ID:

The Kolz ransomware removal should revert these dangerous changes, but we recommend using FortectIntego to fix virus damage repair. It is important to tackle all the areas that malicious programs can affect. So removing the virus, clearing the system should come before any file recovery techniques.

Kolz virus creators keep changing distribution ways to affect more victims each time

In most cases, this infection is spreading via software cracks/keygens or pirated/repacked installers that can be downloaded on the torrent and similar websites.^[3] To avoid ransomware infection in the future, you should stop using unsafe websites that like to distribute software keygens/cracks.

Once inside the system, Kolz starts to prepare for the successful file encryption process. It performs various changes. For example:

• modifies the Windows registry for persistence purposes;
• deletes Shadow Copies to prevent easy data recovery;
• drops malicious files or applications.

After the preparations, Kolz ransomware begins the files encryption process which usually takes just a brief moment. It may take longer if there are a large amount of data on the computer. Malware should show a popup message during this time. This message looks similar to the Windows update prompt, but it is fake and is shown only to prevent victims from interrupting the encryption process.

After the process, ransomware will deliver a _readme.txt ransom note with an explanation about this virus and a possible solution. If your computer is already affected, you should use anti-malware tools and remove Kolz ransomware as soon as possible instead of paying. This threat must be properly detected and terminated. Experts^[4] say that you should not try to provide payment because ransomware creators' claims about decryption tools are not trustworthy. 

Kolz ransomware virus coming on the machine with other threats

Even though the threat came out around the 20th of Septemper, the week after the initial detections and reports were followed by various user reports^[5] with claims about file damage, infection and even relations with particular malware. It was known before that Djvu ransomware family has been introducing AZORult trojan on machines.

Some of the forum posts and users' claim that Glupteba Trojan is additional threat that can be found with the .kolz version. This relation can be indicated by some of the particular detection names for the intruder like Trojan:Win32/Glupteba.DSE!MTB or Trojan.Glupteba.

You should pay close attention to anti-malware detection results, so the list of intruders might indicate how the particular cryptovirus came. Also, it is important to remove the Kolz virus properly, because any leftovers like these trojans, other malware programs can still trigger issues with performance or infection persistence.

.Kolz file recovery options are quite limited if no file backups are available

Keep in mind that the infection of the virus and .kolz extension file encryption are two separate procedures. You will not be able to open affected files just because you successfully eliminated the ransomware. Due to this, ransomware remains one of the most devastating malicious programs in the wild.

The .kolz virus file recovery is extremely limited without backups, although not impossible in some cases. Unfortunately, there is no universal rule that would guarantee that, in your particular case, the decryption process can be successful using alternative methods (besides paying the criminals).

When ransomware infects the computer, it also attempts to contact a remote Command & Control server controlled by hackers. For each of the victims where this process is successful, a unique ID is assigned, which is associated with the whole encryption and decryption process of .kolz files.

It is known, however, that versions of Djvu often failed to contact the servers since they were simply offline. If your data were encrypted during this time frame, your files would be encrypted with an offline ID, which provides a chance of file recovery using Emsisoft's decryption tool.

Since you need to check certain strings to confirm whether your files were encrypted by an offline ID, you should instead download and run the Emsisoft Djvu decryption tool. Unfortunately, if you received a similar message, there is no way to retrieve your files now using this tool:

Error: No key for New Variant online ID: zGFdql6hM5fwiUxSnWic63XlOuDCeoRUhF47vKUA
Notice: this ID appears to be an online ID, decryption is impossible

In case the application reported that your .kolz virus files were locked with and offline ID but could not be decrypted, it means that none of the victims with an offline ID yet paid cybercriminals retrieved the key and shared it with Emsisoft researchers.

Regardless of your particular case, you could first try to retrieve the encrypted data using alternative methods, such as third-party data recovery software or built-in Windows restore features. Note that the success rate of these techniques is also very limited. 

Get rid of the Kolz ransomware and only then try to recover data

If you want to remove Kolz ransomware, you should remember that this virus is similar to other Djvu malware. As previously mentioned, deletion and decryption are different things but you need to get rid of this virus before ane other steps. So, as soon as you see the ransom note on the screen, ignore it and prepare to delete this threat.

First, you should prepare file backups, and think about such instances if you want to have more options in cases like this. If not, you have fewer methods to get those files back after Kolz ransomware removal. Data backups and copies of the affected data are the best when it comes to damaged files. But you should also use a PC repair tool FortectIntego or another system optimizer to repair virus damage in parts of the system.

If you already have backups, then you can remove the Kolz file virus using respectable anti-malware software, for example SpyHunterCombo Cleaner or MalwarebytesMalwarebytes. You may need to enter the Safe Mode if your computer is infected and AV tools cannot run properly. Rely on the information given below.