Advertising technology is at the core of the modern internet economy, something that has turned it into a confusing and increasingly fraught battleground of competing interests. Users don’t like intrusive ads and respond with adblockers, publishers are at war with these blockers to get the ads through while large communications firms are now trying to undermine the whole ad-serving model for strategic reasons.

The ads in question include banners, pop-ups and pop-unders, all of which interrupt websites to the degree that users notice something is happening. It seems that everyone either loves or hates them, or simply wants to control how they are served. A lot is at stake with vast sums of money resting on how the chips land on this one. Google alone can point to almost $60 billion (£40 billion) in revenue from serving ads during 2014 so anything that disrupts this will elicit a strong response.


As we noted in the recent article on privacy tools, adblocking also has security benefits, for instance greatly reducing the hazard of malvertising, which uses pop-up and redirects to point users to malware and worse. In some cases, blocking also benefits privacy by stopping advertisers gathering data on individual browsing habits in order to serve targeted, ’programmatic’ ads.

The contentious issue is how adblocking is implemented. The traditional way is to load a plug-in on each device that allows the user to manage which sites are allowed to show ads and which aren’t. It’s a bit laborious but has still become a growing nuisance for advertisers and the publishers that depend on serving ads but the overall number of users for these tools remains small. In an effort to wean users off them, publishers increasingly throw up polite-sounding messages if they detect a user is browsing with a blocker installed, asking them to consider turning it off.

The question is politely-worded but it’s really a way of reintroducing the hassle that adblockers were supposed to avoid in the first place. Some publishers – The Washington Post and CNET for instance – have even started to drop users who insist on using such tools, a tactic that underscores that this issue is turning into a high-stakes game of chicken.

How adblockers work

All blockers interrupt ads they detect being served from pages but there are different techniques for achieving this. The default and most efficient technique is to block the HTTP ad request as it is made although some instead block content on its return journey. As the example of Three UK demonstrates (see below), ads can also be blocked at carrier network level while it is always possible, with some effort, to block common ad-serving domains using a firewall. It’s never been obvious whether many admins bother to do this.

From the blocking side, stopping advertising can be a complex undertaking and actually pulling it off effectively requires building a maintaining a list of ad platforms, trackers and beacons and applying this in real time to web traffic. These days, the quality of adblocking is high.