How Do Internet Filters Work?

What Are Internet Filters?

As Internet use rose, debate over objectionable content online sparked the introduction of Internet filters. Such filters restricted access to video, images and Web pages based on rules established by parents, schools and businesses. Internet filters are widely available, integrated into popular Web browsers such as Microsoft's Internet Explorer and the freely available Firefox. More elaborate Internet filtering is available as separate applications, such as Netnanny.

Internet filters have a variety of uses--from protecting children, limiting public access to certain sites or material, to restricting when and how employees can use the Internet while at work.

Internet filters work by excluding or including content. These methods are more commonly referred to as a "black list" or "white list." As its name implies, a black list blocks all websites or material restricted by an authority. The reverse, a white list, bars access to all Internet content except items approved by the filter.

Another filtering method checks keywords entered, restricting access or completely blocking an Internet user if she types words such as "sex" or controversial phrases such as "Tiananmen Square." This option has drawn the ire of some who object that this content filtering can block access to valuable information, resources or be used to stifle political dissent.

For Internet Explorer users, there are two ways to enable Internet filtering: by site or by content rating. IE offers five preset Internet safety zones that users can place Web addresses. Each zone has a particular level of trust, ranging from low to high.

The Trusted zone is for websites you're sure won't damage your computer such as your work's intranet, sites from which you've previously downloaded, or companies you've visited. The IE browser provides little security for sites included in this zone.

The Restricted zone is at the other extreme, a security area for websites you don't trust and believe could harm your computer. Sites placed in this category receive medium security while browsing with IE.

The mid-level Internet safety zones are the Internet zone and the Local Intranet Zone. The Internet zone is designed for non-local sites that aren't in any other security category. Sites in the Local Intranet Zone include those that don't follow the usual naming conventions for sites, such as http://local, according to Microsoft.

A more recent Internet filtering method is content labeling. This practice is akin to movie ratings that provide a guide based on a film's content. Unlike filters that use a black or white list, content labeling uses a system developed by the Internet Content Rating Association in 1994. In cooperation with site owners, a file is created that content-filtering applications use to determine whether a site is allowed or blocked.

Unlike IE, the Firefox browser relies on software "extensions" from independent developers. The extensions can block sites based on content or a user-specified time limit.

Firefox filtering extensions include: Glubble, ProCon, LeechBlock and the Jmaxx vulgar word blocker.

Aside from filtering Internet access through the browser, control can also be accomplished through a number of software packages. Some of these include Net Nanny and Safe Eyes.