Remove KOLZ Ransomware (Virus Removal Guide)

kolz ransomware virus removal instructions

KOLZ ransomware aims to encrypt all your personal files

Contents

KOLZ ransomware aims to encrypt all your personal files
What actually was done to your files
Ransomware distribution ways
How to remove KOLZ ransomware virus yourself
- Post-removal steps
Decrypt KOLZ files
Frequently Asked Questions

KOLZ ransomware is a computer virus that encrypts files on victim’s computer using RSA crypto-algorithm. Discovered by M.Gillespie, the virus itself is the 252nd version of STOP/DJVU ransomware family. The malware marks affected data with .kolz file extension during the cyber attack. From that moment, these files can no longer be accessed by the user. Following that, the malware drops _Readme.txt files in every folder to introduce a ransom-demanding message from the criminals. The note tells the victim to contact the criminals by writing to helpmanager@mail.ch or restoremanager@airmail.cc email addresses. The attackers demand to pay from $480 to $980 in Bitcoins for the crypto-malware decryption tool.

Victims of KOLZ virus often report downloading this malware from illegal software downloads. This can happen after browsing on untrustworthy sites promoting peer-to-peer file-sharing (torrents). The encryption process starts immediately once the victim opens a deceitful file. After the virus successfully locks data, users are unable to use it in any way. Usually, it targets the most valuable files, such as videos, photographs, documents, voice memos, etc. Now that the virus has the control of victim’s personal files, it leaves a note with instructions and criminals’ demands of what needs to be done in order to decrypt .KOLZ files.

Do not pay the ransom to the attackers – try the suggested file recovery tools first, as explained in the tutorial we provide.
Scott Bolton

Screenshot of encrypted files and ransom note left by the virus.

What actually was done to your files

KOLZ virus encrypts files with a help of an advanced RSA encryption algorithm and keeps them inaccessible until victim pays the ransom. To give you a better understanding of what encryption means, you must first get to know what cryptography is, and what is the purpose of it. RSA is widely used public-key cryptosystem that allows securing transmitted information on a military-grade level.

The virus encrypts files (valuable information) with unique public encryption key (string). It must be said that for every encryption key, there is a matching decryption key. As a result, in criminals database each victim has a decryption key assigned to the infected host (computer). The criminals suggest purchasing this key along with decryption software for a ransom. Without these keys, decrypting .kolz files is nearly impossible process (in the majority of cases).

Contents of the ransom note left behind

The Readme.txt file that serves as a ransom note explains to users what happened to their computers. The crooks try to comfort people by saying that this is not a big deal and they can easily get back their data. For that, they insist on paying a considerable amount of money — $490 if users contact the criminals and pay the ransom within 72 hours of the infection or $980 later for Kolz ransomware decryptor.

Additionally, they encourage victims to reach out to them via helpmanager@mail.ch or restoremanager@airmail.cc contacts for further instructions. These two emails have been long-used in STOP/DJVU ransomware campaign and provided in ransom notes by the previous variants such as KASP, OGDO, GENO, NPPH, and others.

_readme.txt serves as a ransom note from the cybercriminals.

In our experience, cybercriminals are mainly driven by monetary benefits and rarely appear to be trustworthy. Some of them continue to blackmail people for even more money after they agree to pay or simply disappear after receiving the initial payment. Likewise, there are no guarantees that you will receive the decryption key even if you follow the demands.

Our team suggests you remove KOLZ ransomware virus to avoid financial losses in the first place. Keep in mind that you can always find alternative methods to restore encrypted information. For example, backup copies.

DOWNLOAD RESTORO

Crypto-malware infection symptoms

It is important to mention that ransomware-type infections are highly advanced and often try to operate in stealth mode. This malware is no exception as it shows a fake Windows Update screen as a disguise to hide the encryption process. This way, victims usually fail to identify the infection and do not try to stop the activity. As a result, most of the information on the PC is successfully encrypted and files with .KOLZ extension become useless.

Furthermore, some research shows that this ransomware is capable of modifying the Windows hosts file to block access to certain security websites and antivirus tools. Likewise, users who try to search for help online and run their security programs can face network connectivity issues. If they want to circumvent the modifications, they either must reset Windows hosts file back to default.

Additionally, IT experts warn that this cyber threat does not come alone. In fact, it is programmed to infiltrate a password stealer known as AZORULT once it enters the system. This malicious software is developed to gather credentials from every sign in user performs and transfer them to cybercriminals. That includes collecting email addresses, passwords, usernames, and other sensitive data. Unfortunately, this Trojan remains hidden throughout the whole process. Thus, it is recommended to use RESTORO for virus damage repair along with another professional program for KOLZ ransomware removal to get rid of all malicious applications at once.

Virus summary

Name	KOLZ ransomware
Type	File-encrypting virus, File Locker, Crypto-malware
Family	STOP/DJVU
Variant	252nd
Malicious executive	C5CB.exe, a43a.exe or similar
Other versions	VTYM, KQGS, XCBG, BPQD, EYRV, UIGD, VLFF (find full list here)
Extension	.kolz
Symptoms	Users are provided with an imitation of a Windows update screen to hide the encryption process and successfully complete it; Later, files are marked with the specific extension and can no longer be opened
Ransom note	_Readme.txt
Contacts	helpmanager@mail.ch; restoremanager@airmail.cc
Amount of ransom	$490-$980
Spread	Through illegal downloads on peer-to-peer (P2P) sites
Decryption	The easiest way to get back your data is by using the latest backup copies from the Cloud; Although, there are alternative ways to decrypt files locked by STOP/DJVU ransomware
Removal	Ransomware-type infections should be eliminated using a professional tool, such as RESTORO.

SCAN WINDOWS SYSTEM

See Full Review

Scan your system for FREE to detect security, hardware and stability issues. You can use the scan results and try to remove threats manually, or you can choose to get the full version of software to fix detected issues and repair virus damage to Windows OS system files automatically. Includes Avira spyware/malware detection & removal engine.

Ransomware distribution ways

Ransomware like KOLZ virus are mostly distributed via (P2P) torrent-sharing sites to try find software cracks on download other content illegally. Cybercriminals are aware of such browsing habits and try to exploit them for their own benefit — they disguise ransomware executables as software cracks or keygens. Therefore, while the victim thinks he’s opening a file required for illegal software activation, one actually launches a data-encrypting process.

Additionally, the crooks use specific disguise techniques to distribute this cyber threat. The main one is uploading the executable file with a different name. For example, a well-known software or service provider, such as Adobe. Likewise, when people aim to download a crack or an update for the desired program they get the ransomware instead.

Another very popular technique to spread computer malware is to disguise it as a document and attach it to malicious email spam campaigns (also known as malspam). In such case, the criminals create safe-looking messages that look like they were sent by trustworthy company representatives. Such emails typically urge to open the attached file to view its contents and reply back as soon as possible. The file is often named as invoice, missed or pending payment information/confirmation, or another document. However, once opened, the file can run an inserted malicious script to download the payload from an external source and run it on victim’s PC.

If you want to avoid ransomware attacks, you should download applications from official websites or authorized distribution sources only. Avoid visiting suspicious pages or even getting programs or their updates from annoying pop-ups. Keep in mind that they can contain malicious code and help infiltrate malware. Finally, avoid opening emails that you did not expect to receive, especially if they include suspicious links or attachments that need to be viewed “urgently.”

How to remove KOLZ ransomware virus yourself

Kolz ransomware removal requires attention to detail in order to ensure safe malware elimination. For that, you must get robust and reliable tools to identify, locate, and uninstall malware-related components. If you manage to get rid of all ransomware elements, this cyber threat will not reappear on the system shortly after the removal.

The easiest way to remove KOLZ ransomware virus with all its elements is to get help from professional security programs. They are designed to quickly find all files related to the file-encrypting virus and delete them without causing any further damage. We recommend using RESTORO as it can help optimize the system after the attack as well.

Post-removal steps

Once you complete the elimination, you can start thinking about ways to restore the affected data. You can either try using backups or check out the STOP/DJVU Decryption Tool that has been released. It might help to deal with certain versions of the malware.

It is EXTREMELY IMPORTANT to change all your passwords after deleting the ransomware and other threats using an automated malware removal program. Please pay special attention to passwords saved in your web browsers. As mentioned earlier, the ransomware installs AZORULT password stealer, which tends to grab login credentials saved in your Chrome, Firefox and other web browsers.

Finally, you might discover that you cannot access specific websites online after KOLZ ransomware attack. It is so because the virus modifies Windows HOSTS file in order to block a list of computer security-related domains. To revert this HOSTS file back to default, follow our guide here.

OUR GEEKS RECOMMEND

Our team recommends a two-step rescue plan to remove ransomware and other remaining malware from your computer, plus repair caused virus damage to the system:

STEP 1. REMOVE AUTOMATICALLY WITH ROBUST ANTIVIRUS

REMOVE & PROTECT WITH INTEGO

Get INTEGO ANTIVIRUS for Windows to remove ransomware, Trojans, adware and other spyware and malware variants and protect your PC and network drives 24/7.. This VB100-certified security software uses state-of-art technology to provide protection against ransomware, Zero-Day attacks and advanced threats, Intego Web Shield blocks dangerous websites, phishing attacks, malicious downloads and installation of potentially unwanted programs.

Use INTEGO Antivirus to remove detected threats from your computer.

Read full review here.

STEP 2. REPAIR VIRUS DAMAGE TO YOUR COMPUTER

DOWNLOAD RESTORO

RESTORO provides a free scan that helps to identify hardware, security and stability issues and presents a comprehensive report which can help you to locate and fix detected issues manually. It is a great PC repair software to use after you remove malware with professional antivirus. The full version of software will fix detected issues and repair virus damage caused to your Windows OS files automatically.

RESTORO uses AVIRA scanning engine to detect existing spyware and malware. If any are found, the software will eliminate them.

Read full review here.

GeeksAdvice.com editors select recommended products based on their effectiveness. We may earn a commission from affiliate links, at no additional cost to you. Learn more.

KOLZ ransomware virus Removal Guidelines

Method 1. Enter Safe Mode with Networking

Step 1. Start Windows in Safe Mode with Networking

Before you try to remove KOLZ ransomware virus virus, you must start your computer in Safe Mode with Networking. Below, we provide the easiest ways to boot PC in the said mode, but you can find additional ones in this in-depth tutorial on our website – How to Start Windows in Safe Mode. Also, if you prefer a video version of the tutorial, check our guide How to Start Windows in Safe Mode on Youtube.

Instructions for Windows XP/Vista/7 users

First of all, turn off your PC. Then press the Power button to start it again and instantly start pressing F8 button on your keyboard repeatedly in 1-second intervals. This launches the Advanced Boot Options menu.
Use arrow keys on the keyboard to navigate down to Safe Mode with Networking option and press Enter.

Instructions for Windows 8/8.1/10/11 users

Open Windows Start menu, then press down the Power button. On your keyboard, press down and hold the Shift key, and then select Restart option.
This will take you to Windows Troubleshoot screen. Choose Troubleshoot > Advanced Options > Startup Settings > Restart. Tip: If you can't find Startup Settings, click See more recovery options.
In Startup Settings, press the right key between F1-F9 to enter Safe Mode with Networking. In this case, it is the F5 key.

Step 2. Remove files associated with the virus

Now, you can search for and remove KOLZ ransomware virus files. It is very hard to identify files and registry keys that belong to the ransomware virus, Besides, malware creators tend to rename and change them repeatedly. Therefore, the easiest way to uninstall such type of a computer virus is to use a reliable security program such as INTEGO Antivirus, which also includes data recovery software. For virus damage repair, consider using RESTORO.

Special Offer

DOWNLOAD AND SCAN

Compatibility: Microsoft Windows
See Full Review

RESTORO is a unique PC Repair Tool which comes with an in-built Avira scan engine to detect and remove spyware/malware threats and uses a patented technology to repair virus damage. The software can repair damaged, missing or malfunctioning Windows OS files, corrupted DLLs, and more. The free version offers a scan that detects issues. To fix them, license key for the full software version must be purchased.

Method 2. Use System Restore

In order to use System Restore, you must have a system restore point, created either manually or automatically.

Step 1. Boot Windows in Safe Mode with Command Prompt

Instructions for Windows XP/Vista/7 users

Shut down your PC. Start it again by pressing the Power button and instantly start pressing F8 button on your keyboard repeatedly in 1-second intervals. You will see Advanced Boot Options menu.
Using arrow keys on the keyboard, navigate down to Safe Mode with Command Prompt option and press Enter.

Instructions for Windows 8/8.1/10/11 users

Launch Windows Start menu, then click the Power button. On your keyboard, press down and hold the Shift key, and then choose Restart option with the mouse cursor.
This will take you to Windows Troubleshoot screen. Choose Troubleshoot > Advanced Options > Startup Settings > Restart. Tip: If you can't find Startup Settings, click See more recovery options.
In Startup Settings, press the right key between F1-F9 to enter Safe Mode with Command Prompt. In this case, press F6 key.

Step 2. Start System Restore process

Wait until system loads and command prompt shows up.
Type cd restore and press Enter, then type rstrui.exe and press Enter. Or you can just type %systemroot%system32restorerstrui.exe in command prompt and hit Enter.
This launches System Restore window. Click Next and then choose a System Restore point created in the past. Choose one that was created before ransomware infection.
Click Yes to begin the system restoration process.

After restoring the system, we recommend scanning the system with antivirus or anti-malware software. In most cases, there won't be any malware remains, but it never hurts to double-check. In addition, we highly recommend checking ransomware prevention guidelines provided by our experts in order to protect your PC against similar viruses in the future.

Alternative software recommendations

Malwarebytes Anti-Malware

Removing spyware and malware is one step towards cybersecurity. To protect yourself against ever-evolving threats, we strongly recommend purchasing a Premium version of Malwarebytes Anti-Malware, which provides security based on artificial intelligence and machine learning. Includes ransomware protection. See pricing options and protect yourself now.

System Mechanic Ultimate Defense

If you're looking for an all-in-one system maintenance suite that has 7 core components providing powerful real-time protection, on-demand malware removal, system optimization, data recovery, password manager, online privacy protection and secure driver wiping technology. Therefore, due to its wide-range of capabilities, System Mechanic Ultimate Defense deserves Geek's Advice approval. Get it now for 50% off. You may also be interested in its full review.

Disclaimer. This site includes affiliate links. We may earn a small commission by recommending certain products, at no additional cost for you. We only choose quality software and services to recommend.

Decrypt KOLZ files

Fix and open large KOLZ files easily:

It is reported that STOP/DJVU ransomware versions encrypt only the beginning 150 KB of each file to ensure that the virus manages to affect all files on the system. In some cases, the malicious program might skip some files at all. That said, we recommend testing this method on several big (>1GB) files first.

Create a copy of encrypted file to a separate folder using Copy > Paste commands.
Now, right-click the created copy and choose Rename. Select the KOLZ extension and delete it. Press Enter to save changes.
In the prompt asking whether you want to make the changes as file might become unusable, click OK.
Try opening the file.

STOP/DJVU decryption tool usage guide

STOP/DJVU ransomware versions are grouped into old and new variants. KOLZ ransomware virus is considered the new STOP/DJVU variant, just like VTYM, KQGS, XCBG, BPQD, EYRV, UIGD, VLFF (find full list here). This means full data decryption is now possible only if you have been affected by offline encryption key. To decrypt your files, you will have to download Emsisoft Decryptor for STOP DJVU, a tool created and maintained by a genius security researcher Michael Gillespie.

Note! Please do not spam the security researcher with questions whether he can recover your files encrypted with online key - it is not possible.

In order to test the tool and see if it can decrypt KOLZ files, follow the given tutorial.

Download the decryption tool from Emsisoft.
Click the little arrow next to your download and choose Show in Folder.
Now, right-click the file and choose Run as Administrator. If asked, enter administrator's password.
In UAC window, click Yes.
Click Yes to agree to software terms in both windows.
The tool will automatically include C:// disk as a location to decrypt. The file recovery tool will prepopulate the locations to scan, including connected data storage drives or network drives. Click Add folder if you wish to add additional locations.
In Options tab, you can choose to keep encrypted file copies. We recommend leaving this option selected, especially if you do not know if the decryption tool will work.
Click Decrypt to start restoring KOLZ files. You will see the progress in the Results tab. Here, you can see messages from the tool, such as whether the decryption procedure is successful, or you need to wait for an update.
You might also be informed that online key was used to encrypt your files. In such case, the decryption tool won't work for you, and the only way to recover your files is to use a data backup.

Meanings of decryptor's messages

The KOLZ decryption tool might display several different messages after failed attempt to restore your files. You might receive one of the following messages:

Error: Unable to decrypt file with ID: [example ID]

This message typically means that there is no corresponding decryption key in the decryptor's database.

No key for New Variant online ID: [example ID]
Notice: this ID appears to be an online ID, decryption is impossible

This message informs that your files were encrypted with online key, meaning no one else has the same encryption/decryption key pair, therefore data recovery without paying the criminals is impossible.

Result: No key for new variant offline ID: [example ID]
This ID appears to be an offline ID. Decryption may be possible in the future.

If you were informed that an offline key was used, but files could not be restored, it means that the offline decryption key isn't available yet. However, receiving this message is extremely good news, meaning that it might be possible to restore your KOLZ extension files in the future. It can take a few months until the decryption key gets found and uploaded to the decryptor. We recommend you to follow updates regarding the decryptable DJVU versions here. We strongly recommend backing up your encrypted data and waiting.

Report Internet crime to legal departments

Victims of KOLZ ransomware virus should report the Internet crime incident to the official government fraud and scam website according to their country:

In the United States, go to the On Guard Online website.
In Australia, go to the SCAMwatch website.
In Germany, go to the Bundesamt für Sicherheit in der Informationstechnik website.
In Ireland, go to the An Garda Síochána website.
In New Zealand, go to the Consumer Affairs Scams website.
In the United Kingdom, go to the Action Fraud website.
In Canada, go to the Canadian Anti-Fraud Centre.
In India, go to Indian National Cybercrime Reporting Portal.
In France, go to the Agence nationale de la sécurité des systèmes d’information.

If you can't find an authority corresponding to your location on this list, we recommend using any search engine to look up "[your country name] report cyber crime". This should lead you to the right authority website. We also recommend staying away from third-party crime report services that are often paid. It costs nothing to report Internet crime to official authorities.

Another recommendation is to contact your country's or region’s federal police or communications authority.

Frequently Asked Questions

✓ How can I open .KOLZ files?

You can only open KOLZ files if you have the decryption key, or if you were affected by offline encryption type.

✓ How do I know if my files were encrypted with offline or online encryption?

To figure out whether you were affected by offline encryption, please go to C:/SystemID/PersonalID.txt and see if the string inside of it ends in t1. You can also try using Emsisoft Decryptor for STOP/DJVU.

✓ My files contain very important information (family memories). Every tool I used says it is impossible to decrypt. What should I do?

Please follow the guidances provided by the official KOLZ decryption tools and believe what they say. If they say it is impossible to decrypt, it really is so. There is no magic tool or human capable of decrypting your files hiding somewhere. Encryption is a technique created to be nearly impossible to decrypt without a special private key (held by the criminals).

✓ I am afraid virus is still in my computer system. What should I do?

We advise scanning with anti-virus, anti-malware, malware removal tools or software like RESTORO to eliminate virus damage on the system. If you do not trust using a single tool, try running one after another. However, we do not recommend keeping several security programs on a computer at once as they can interfere with each other's work.

✓ I saw several Youtube videos suggesting secret decryption tools. Can I trust them?

Beware of fake KOLZ decryption tools circulating around the web. Cyber criminals are uploading them to various shady websites, also might be promoting them via suspicious Youtube videos. These programs can infect your computer even more heavily (Trojans, miners, etc.). We suggest being extremely cautious around the web. If there will be an official STOP/DJVU decryption tool available, it will be widely discussed in public media.

Scott Bolton

Scott Bolton is a senior content strategist in our Geek’s Advice team. He is exceptionally passionate about covering the latest information technology themes and inspire other team members to follow new innovations. Despite the fact that Scott is an old-timer among the Geeks, he still enjoys writing comprehensive articles about exciting cybersecurity news or quick tutorials.