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Adblockers explained: Inside the menace that stalks publishing

John E Dunn | March 7, 2016
Adblocking tools have turned into the feared gatekeepers of web advertising.

Today, browsing adblockers sit plumb in the middle of an increasingly tense online stand-off between software firms, online advertisers and the web publishing industry which makes it hard to imagine their innocuous beginnings in the early 2000s.

Marketed for years by a cottage industry of coders, adblockers were just another browser utility, one of many users could choose from for all sorts off tasks. Most users didn't use them or hadn't even heard of them. From the outside, it was never clear whether they worked or were even particularly necessary.

Five or six years ago, something changed, although not everyone noticed at the time. Publishers with under-pressure business models started allowing more intrusive ads that splashed pop-ups, consumed bandwidth and made browsing online content more time-consuming. The clutter of third-party platforms serving these ads started out-doing each other in their attempts to attract, track and even follow users in order to target them using programmatic advertising.

It shouldn't have been a surprise that a growing number of users rebelled by using adblockers which were capable of stopping at least some of these ads and third-party tracking cookies. The trend has accelerated to the present day even though the fashion for intrusive advertising has abated. Aggressive ads are now the exception than the rule but adblockers are more common and effective than ever and it's not hard to imagine a world where almost everyone users them for mobile as well as desktop browsers.

The genie is now long gone from a bottle publishers and ad networks hadn't realised they were opening.

Adblockers explained - adblockers in action

How does this software work? Desktop adblockers work as browser extensions, a simple and relatively lightweight way of using software that is very easy to install and uninstall. When working, a number of techniques come into play including hardcoded lists of blacklisted URLs, by blocking known elements such as Flash and autoplay and using rule-based filter lists, of which there are numerous examples. When the user visits a webpage, adblockers act as gatekeepers intercepting and applying rules to the outgoing HTTP or HTTPS requests, stopping them from reaching the ad-serving platform in question. Less commonly, the filtering is done on the return path. Some techniques are undocumented but there is no doubt that some of them are intrusive, analysing and interfering with numerous elements on webpages.

Modern browsers such as Firefox, Chrome and IE offer a basic set of these controls (e.g. over Flash and pop-ups) but are never as comprehensive as an adblocker.

Adblockers don't just control the visible elements of websites but, perhaps more significantly, the invisible parts too. A subset of adblockers offer privacy controls (blocking third-party cookie tracking and targeted advertising) and beacons while a few replicate the anti-phishing protection that is already built into big browser platforms.

 

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