Home > Trojan > Critical Firefox Update (firefox-patch.js) Virus Scam – How to Remove It

Critical Firefox Update (firefox-patch.js) Virus Scam – How to Remove It

This article has been created to explain what is the Critical Firefox Update virus and how to stop such malicious redirects to dangerous pages in the future.

A new redirect web page which tries to infect victim computers with malware via JavaScript file, called firefox-patch.js. The redirect page aims to convince users that they should immediately update their version of Firefox and display a pop-up which automatically shows a prompt to save the patch file or automatically open it. The JavaScript file itself is reported by security researchers to be a well-known Trojan Horse infection, going by the name Kovter, which was reported mainly to be associated with such fake updates as a mean of distribution. If you believe that your computer has been infected by the Kovter Trojan or if you keep seeing the “Critical Firefox Update” screen appearing, we recommend that you read the following article as it aims to help you secure your computer.

Threat Summary

Name Critical Firefox Update (Kovter Malware)
Type Trojan
Short Description Displayed by a fake web page, the Kovter trojan aims to steal information from the infected computers.
Symptoms Your web browser may display a web-page , headed “Critical Firefox Update”. It asks you to download a .js file, which is the malware infection module.
Distribution Method Via a fake Firefox Update page.
Detection Tool See If Your System Has Been Affected by malware


Malware Removal Tool

User Experience Join Our Forum to Discuss Critical Firefox Update (Kovter Malware).

Critical Firefox Update Page – Distribution Methods

In order for you, the user to see it, the Critical Firefox Update page may be spread as a result of either visiting a web page, which causes a redirect to it or as a result of having adware or a similar unwanted program on your computer.

If it infects your computer as a result of a web page, then be advised that this page is either malicious or a compromised legitimate one. It often happens that cyber-criminals tend to intercept traffic from legitimate web pages to display their redirects and infect victims and they often target sites with bad security practices.

If however you see all sorts of redirects and pop-ups of such type, then it is very likely that you may have started seeing this web page as a result of having a PUP (potentially unwanted program) that is install on your OS. These types of PUPs often pretend to be legitimate helper programs, but their main goal is to display ads that generate money to their developers via suspicious pay-per-click schemes.

Critical Firefox Update and Kovter Trojan – More Information

When you see the Critical Firefox Update page, you may immediately notice a pop-up alongside it, asking you to download firefox-patch.js:

This .js file is the infection file of the Kovter Trojan horse. The Kovter Trojan is a threat that exists since the first appearances of the Police type of ransomare viruses. The virus has evolved in a more sophisticated variant since then that injects a JavaScript code onto victims computers.

When an infection with Kovter malware commences, the virus first triggers a dropper which drops malicious files in %AppData% and %Local% directories. This activity results in the Kovter malware being able to create a registry entry that triggers a maicious shell code in Widnows PowerShell and causes a restart, sealing it’s infectionas successful. The outcome of this after Kovter restarts is a file, called regsvr32.exe or similar fake Windows process name to run with administrative priveleges on the infected machine.

The outcome of this is that Kovter is capable to perform the following activities on a compromised computer:

  • Display advertisements and connect the victim PC to various third-party hosts.
  • Take screenshots on the compromised machine.
  • Obtain passwords.
  • Steal files from the computer it has infected.
  • Record sound or video from the camera and microphone.
  • Log the keystrokes you type.

Remove Critical Firefox Update and Kovter Troaj from Windows

If you want to remove the Kovter Trojan from Windows, we strongly suggest that you follow the removal instructions underneath this article. They have been divided in manual as well as automatic removal instructions with their main goal being to help you remove this virus according to your personal experience and preferences, concerning malware removal. Furthermore, if manual removal does not seem to be helpful, an automatic removal is also strongly advisable. According to security experts, the most effective method for automatic removal is to download and run a scan using an advanced anti-malware software. It will help you to automatically remove the Kovter malware and the software that may be causing such redirections to appear on your PC and also ensure that future protection is also available.

Ventsislav Krastev

Ventsislav is a cybersecurity expert at SensorsTechForum since 2015. He has been researching, covering, helping victims with the latest malware infections plus testing and reviewing software and the newest tech developments. Having graduated Marketing as well, Ventsislav also has passion for learning new shifts and innovations in cybersecurity that become game changers. After studying Value Chain Management, Network Administration and Computer Administration of System Applications, he found his true calling within the cybersecrurity industry and is a strong believer in the education of every user towards online safety and security.

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Preparation before removing Critical Firefox Update (Kovter Malware).

Before starting the actual removal process, we recommend that you do the following preparation steps.

  • Make sure you have these instructions always open and in front of your eyes.
  • Do a backup of all of your files, even if they could be damaged. You should back up your data with a cloud backup solution and insure your files against any type of loss, even from the most severe threats.
  • Be patient as this could take a while.
  • Scan for Malware
  • Fix Registries
  • Remove Virus Files

Step 1: Scan for Critical Firefox Update (Kovter Malware) with SpyHunter Anti-Malware Tool

1. Click on the "Download" button to proceed to SpyHunter's download page.

It is recommended to run a scan before purchasing the full version of the software to make sure that the current version of the malware can be detected by SpyHunter. Click on the corresponding links to check SpyHunter's EULA, Privacy Policy and Threat Assessment Criteria.

2. After you have installed SpyHunter, wait for it to update automatically.

SpyHunter 5 Scan Step 1

3. After the update process has finished, click on the 'Malware/PC Scan' tab. A new window will appear. Click on 'Start Scan'.

SpyHunter 5 Scan Step 2

4. After SpyHunter has finished scanning your PC for any files of the associated threat and found them, you can try to get them removed automatically and permanently by clicking on the 'Next' button.

SpyHunter 5 Scan Step 3

If any threats have been removed, it is highly recommended to restart your PC.

Step 2: Clean any registries, created by Critical Firefox Update (Kovter Malware) on your computer.

The usually targeted registries of Windows machines are the following:

  • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
  • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
  • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce
  • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce

You can access them by opening the Windows registry editor and deleting any values, created by Critical Firefox Update (Kovter Malware) there. This can happen by following the steps underneath:

1. Open the Run Window again, type "regedit" and click OK.
Remove Virus Trojan Step 6

2. When you open it, you can freely navigate to the Run and RunOnce keys, whose locations are shown above.
Remove Virus Trojan Step 7

3. You can remove the value of the virus by right-clicking on it and removing it.
Remove Virus Trojan Step 8 Tip: To find a virus-created value, you can right-click on it and click "Modify" to see which file it is set to run. If this is the virus file location, remove the value.

Step 3: Find virus files created by Critical Firefox Update (Kovter Malware) on your PC.

1.For Windows 8, 8.1 and 10.

For Newer Windows Operating Systems

1: On your keyboard press + R and write explorer.exe in the Run text box and then click on the Ok button.

Remove Virus Trojan Step 9

2: Click on your PC from the quick access bar. This is usually an icon with a monitor and its name is either “My Computer”, “My PC” or “This PC” or whatever you have named it.

Remove Virus Trojan Step 10

3: Navigate to the search box in the top-right of your PC's screen and type “fileextension:” and after which type the file extension. If you are looking for malicious executables, an example may be "fileextension:exe". After doing that, leave a space and type the file name you believe the malware has created. Here is how it may appear if your file has been found:

file extension malicious

N.B. We recommend to wait for the green loading bar in the navigation box to fill up in case the PC is looking for the file and hasn't found it yet.

2.For Windows XP, Vista, and 7.

For Older Windows Operating Systems

In older Windows OS's the conventional approach should be the effective one:

1: Click on the Start Menu icon (usually on your bottom-left) and then choose the Search preference.

Remove Virus Trojan

2: After the search window appears, choose More Advanced Options from the search assistant box. Another way is by clicking on All Files and Folders.

Remove Virus Trojan Step 11

3: After that type the name of the file you are looking for and click on the Search button. This might take some time after which results will appear. If you have found the malicious file, you may copy or open its location by right-clicking on it.

Now you should be able to discover any file on Windows as long as it is on your hard drive and is not concealed via special software.

Critical Firefox Update (Kovter Malware) FAQ

What Does Critical Firefox Update (Kovter Malware) Trojan Do?

The Critical Firefox Update (Kovter Malware) Trojan is a malicious computer program designed to disrupt, damage, or gain unauthorized access to a computer system.

It can be used to steal sensitive data, gain control over a system, or launch other malicious activities.

What Damage Can Critical Firefox Update (Kovter Malware) Trojan Cause?

The Critical Firefox Update (Kovter Malware) Trojan is a malicious type of malware that can cause significant damage to computers, networks and data.

It can be used to steal information, take control of systems, and spread other malicious viruses and malware.

Is Critical Firefox Update (Kovter Malware) Trojan a Harmful Virus?

Yes, it is. A Trojan is a type of malicious software that is used to gain unauthorized access to a person's device or system. It can damage files, delete data, and even steal confidential information.

Can Trojans Steal Passwords?

Yes, Trojans, like Critical Firefox Update (Kovter Malware), can steal passwords. These malicious programs are designed to gain access to a user's computer, spy on victims and steal sensitive information such as banking details and passwords.

Can Critical Firefox Update (Kovter Malware) Trojan Hide Itself?

Yes, it can. A Trojan can use various techniques to mask itself, including rootkits, encryption, and obfuscation, to hide from security scanners and evade detection.

Can a Trojan be Removed by Factory Reset?

Yes, a Trojan can be removed by factory resetting your device. This is because it will restore the device to its original state, eliminating any malicious software that may have been installed.

Can Critical Firefox Update (Kovter Malware) Trojan Infect WiFi?

Yes, it is possible for a Trojan to infect WiFi networks. When a user connects to the infected network, the Trojan can spread to other connected devices and can access sensitive information on the network.

Can Trojans Be Deleted?

Yes, Trojans can be deleted. This is typically done by running a powerful anti-virus or anti-malware program that is designed to detect and remove malicious files. In some cases, manual deletion of the Trojan may also be necessary.

Can Trojans Steal Files?

Yes, Trojans can steal files if they are installed on a computer. This is done by allowing the malware author or user to gain access to the computer and then steal the files stored on it.

Which Anti-Malware Can Remove Trojans?

Anti-malware programs such as SpyHunter are capable of scanning for and removing Trojans from your computer. It is important to keep your anti-malware up to date and regularly scan your system for any malicious software.

Can Trojans Infect USB?

Yes, Trojans can infect USB devices. USB Trojans typically spread through malicious files downloaded from the internet or shared via email, allowing the hacker to gain access to a user's confidential data.

About the Critical Firefox Update (Kovter Malware) Research

The content we publish on SensorsTechForum.com, this Critical Firefox Update (Kovter Malware) how-to removal guide included, is the outcome of extensive research, hard work and our team’s devotion to help you remove the specific trojan problem.

How did we conduct the research on Critical Firefox Update (Kovter Malware)?

Please note that our research is based on an independent investigation. We are in contact with independent security researchers, thanks to which we receive daily updates on the latest malware definitions, including the various types of trojans (backdoor, downloader, infostealer, ransom, etc.)

Furthermore, the research behind the Critical Firefox Update (Kovter Malware) threat is backed with VirusTotal.

To better understand the threat posed by trojans, please refer to the following articles which provide knowledgeable details.

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