Why Firefox Redirects to a Different Website

Firefox participates in redirection, as do other browser types.

Redirects divert visitors from an address where a Web page has been deleted to the new address where that file can be found. Firefox is programmed to implement redirects when notified by a Web server. However, malicious programs can also hijack Firefox to implement unwanted redirects.

Redirects

Without redirects, Web surfers would frequently encounter “page not found” error screens. This is because Web addresses, called Uniform Resource Locators or URLs, have to be very precise. If one element of a URL changes, then the old address cannot reach it. This is why standard browser errors screens say “page not found” or “page cannot be displayed” rather than “page does not exist.” The page may well exist, just not at the given address. The website's administrator can institute a redirect in the console of the website to compensate for any name changes. That way, any browser requesting the altered address will immediately be notified of the correct address.

Method

Browsers, like Firefox, implement most redirects. Although there are methods for redirects implemented inside the old web page, the most common method is to use an HTTP code, because this does not require maintaining a page at the old address. HTTP is the Hypertext Transfer Protocol and it defines a message structure that enables Firefox, and other Web browsers to request a Web page and also for Web servers to deliver them. If no redirect is in place, the server automatically sends back a message with a 404 code. This means “page not found.” If a redirect has been ordered, the server sends back one of two redirect codes.

Firefox Actions

Redirects by HTTP codes require that the browser implements the redirect. Rather than the code of the Web page, Firefox receives back a message with an empty body, but with either a 301 or 302 code. In each case, the code is followed by a URL. The 301 code indicates a permanent redirect. Firefox applies to the given address for the Web page, but also stores the new address. If it is ever asked to go to the old address again, it will automatically switch to the new address. A 302 code is as temporary redirect. Firefox uses the new address once only and will use the old address for all future requests.

Malicious Redirects

A redirect is supposed to take the user to exactly the same page that the original address held before the page was moved. If the user is redirected to an unrelated page, however, then it is likely that a virus or a Trojan has infected the browser. This type of behavior is typical of adware. The creators of adware make money by charging sites to drive traffic towards them. They create this traffic by hijacking browsers. In Firefox, these adware program usually hide themselves as “add-ons.” Progressively deleting add-ons usually stops the problem.

References

• Practical eCommerce; 6 Reasons to Use URL Redirects; Michael Stearns; November 2010
• SEO Company: URL Redirect
• Symantec; An Offer Too Good to Refuse, Courtesy of Vundo; Hon Lau; May 2010
• Symantec: Backdoor.Tidserv
• Microsoft Malware Protection Center: Virus:Win32/Alureon.H
• Spillspace; New Firefox Virus Causes Redirects to Adsites; February 2009