Troubleshoot Firefox issues caused by malware

Revision Information
  • Revision id: 689
  • Created:
  • Creator: Chris Ilias
  • Comment: added formatting to "extensions installed which you aren't aware of" section
  • Reviewed: No
  • Ready for localization: Yes
  • Readied for localization by: AnonymousUser
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Malware is short for "Malicious Software". It is a term generally used for software installed on your computer that is designed to infiltrate or damage a computer system without the owner's informed consent. Computer viruses, worms, trojan horses, most rootkits, spyware, dishonest adware are different types of malware. Sometimes a problem with Firefox may be a result of malware installed on your computer, that you may not be aware of.

General prevention

Installation of malicious software usually takes advantage of known security vulnerabilities in other software, which may have been patched in later versions. Make sure you are using the latest version of each piece of software you use, including Windows updates.

Run Anti-virus and spyware scanner tools on your system.

Misleading pop-up windows

Many malicious websites try to install malware on your system by making images look like pop-up windows, or displaying an animation of the website scanning your computer. There are two ways to detect this:

Are there extensions installed which you aren't aware of?

  1. At the top of the Firefox windowOn the menu bar, click on click on the Tools menu and select Add-ons. The Add-ons window will open.
  2. Select the Extensions panel.

If Adobe Flash Player 0.2. is listed, you have been infected with the JS_EBOD.A trojan. For information on how to remove it, read the Trend Micro JS_EBOD.A page.

Did you have to pay to download and install Firefox?

Mozilla Firefox is free. If you had to pay for Firefox, or provide any credit card information, the website you used to downloaded Firefox used the Firefox name to con you. To prevent this, always download Firefox from the Mozilla website.

Did you install Firefox from anywhere other than the Mozilla website?

There are some websites that legitimately offer Firefox; but many are not trustworthy. If you downloaded Firefox from anywhere other than the Mozilla website, it is possible that the installer for Firefox you downloaded was different from the official version; and may contain malware. To prevent this, always download Firefox from the Mozilla website or a website you already trust.

Did Firefox come bundled with other software?

Firefox does not come bundled with other software. If you were asked or forced to install something in addition to Firefox, when you tried to install Firefox, it may be malware. To prevent this, always download Firefox from the Mozilla website.

Are you unable to block certain websites?

Firefox will not prevent you from blocking any website. If you are being disallowed from blocking certain websites, malware may be preventing you from blocking that certain website, in order to feed you content from that website.

Do you get an error message when you start Firefox, telling you to use Internet Explorer?

A virus is known to cause this message. For more information, see Use Internet Explorer messages upon Firefox startup.

Getting rid of malware

The website has good information on removing malware. See - How can I get rid of badware?

Please report misuse of the Firefox trademark using the Mozilla Violating Website Report page