Ad filtering

Ad filtering or ad blocking is removing or altering advertising content in a Web page. Advertising can exist in a variety of forms including pictures, animations, text, or pop-up windows. More advanced filters allow fine-grained control of advertisements through features such as blacklists, whitelists, and regular expression filters. Certain security features also have the effect of disabling some ads.

The immediate benefits include quicker loading and cleaner looking Web pages free from advertisements, and lower resource waste (bandwidth, CPU, memory, etc.).

Browser Integration

File:Compaadblocker.png

Wikitravel with and without Adblock Plus

Almost all modern web browsers include a pop-up blocker. Opera, Konqueror, and Internet Explorer 8 also include content filtering, which prevents external files such as images or JavaScript files from loading. Content filtering can be added to Mozilla Firefox and related browsers with Adblock Plus, and a number of sources provide regularly updated filter lists. For Internet Explorer there are several add-ons available like IE7Pro, Adblock Pro and Quero that also allows users to temporarily unblock blocked content. For Chrome, that have extensions available since v2.0, there are AdSweep and FlashBlock extensions available. Another method for filtering advertisements uses CSS rules to hide specific HTML and XHTML elements.

External programs

A number of external applications offer ad filtering as a primary or additional feature. A traditional solution is to customize an HTTP proxy (or web proxy) to filter content. These programs work by caching and filtering content before it is displayed in a user's browser. This provides an opportunity to remove not only ads but also content which may be offensive, inappropriate, or simply junk. Popular proxy software which blocks content effectively include Privoxy, Squid, Proximodo, Adextinguisher, Ad Muncher, Death 2 Ads, Guidescope and Proxomitron. The main advantage of the method is freedom from implementation limitations (browser, working techniques) and centralization of control (the proxy can be used by many users). The major drawback is that the proxy sees only raw content and thus it's difficult to handle JavaScript-generated content.

Hosts file

Further information: hosts file.

This method exploits the fact that most operating systems store a file with IP address, domain name pairs which is consulted by most browsers before using a DNS server to look up a domain name. By assigning the local 127.0.0.1 IP number to known ad servers the user directs traffic intended to reach those ad servers to the local machine. Running a suitable web server locally the ad content can be replaced with anything the user wishes. For instance if the web server sends a blank html page for any request the ads completely disappear from the pages they were originally intended to appear on [1].

DNS Filtering

Advertising can be blocked by using a DNS server which is configured to block access to domains or hostnames which are known to serve ads. Examples are AdBarricade, DNS Redirector, and DNSKong.

See also

• Adversarial information retrieval
• Hosts file filtering
• Proxy server#Content filter
• Proxomitron

Common advertising techniques

• Pop-up ads
• Plain text
• Ad banners
• Flash animations
• Keyword hyperlinks (for example Vibrant Media's IntelliTXT)
• Browser plugins/extensions (often labeled as adware)
• External applications (see adware, spyware)

External links

• DoubleClick Warns Against Ad-Blocking Browsers
• Ad blocking with ad server hostnames
• Ad blocking with local minimal web server