Adblockers are software products which serve to filter out advertising on websites. In addition to banner ads, pop-ups can be blocked, animations can be hidden, and ads identified in texts.

## Development

The first adblockers for Internet applications emerged in 1999. The “Webwasher Classic” software was the pioneer in this area. It was installed locally on your computer as proxy through which Internet content was retrieved. Any ads and pop-ups were filtered out.

This free application was later acquired by McAfee and is today called “McAfee Web Gateway” as a security solution for companies to filter URLs, as an anti-virus solution for Internet and email applications and SSL scanning. However, older versions of Webwasher can still be used free of charge. Other common adblockers include AdBlock, Adblock Plus, and Proxomitron.

Adblockers cannot differentiate one ad from another as far as content is concerned. Instead, they filter based on special features that typically would be contained in ads. Possible approaches for adblockers are:

• The size of the ad graphics, which is mostly standardized (e.g. 300 x 250 pixels = medium rectangle, 120 x 600 skyscraper)
• The URL of the advertisement (collection in black and white lists)