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My understanding of how ad blockers work is essentially that they just look at the domains sending the information. Why has no one been able defeat ad blocking software in a general sense?

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  • As this is asked at the level of a practical security rather than the underlying science, I am migrating this question to Information Security. Nov 26, 2015 at 12:49
  • I imagine that ad blockers regularly have their domain lists updated.
    – Confuto
    Nov 26, 2015 at 12:56

3 Answers 3

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That seems like a fairly outdated take on ad-blockers. There are a lot of different methods that they could use: prevent domain access, restrict known tracking scripts, restrict images of known advert sizes, restrict HTML elements with specific IDs or class names, disable types of active content (e.g. Flash) until the user chooses to load it...

Also, the authors of ad-blocking software tend to be very quick to react to changes made by advert publishers - they can push out updates on the same day if desired. On the other hand, advert publishers are usually running on much longer lead times - weeks or months, depending on the sites they affect.

Finally, ad-blocking has a lot more public support than advertising, at the moment, probably down to concerns with privacy issues and tracking. People don't like adverts "following" them around - Google even warns about this, whilst providing the tools to do it - and are realising that large numbers of adverts slow pages down. Therefore, they will report any adverts that do get through to the ad-block providers, whereas they are unlikely to tell an advertiser "well done, you got through my ad block".

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Adblocking works by either modifying the existing page so that it does not even attempt to load ads or by blocking the domains associated with ad-networks. From inside the current page there is nothing you can do against some extension or proxy denying access to a host, because this is simply outside of what you can do with HTML and Javascript. You could also not simply serve your ads from different hosts because this would need fundamental changes on the way ads are delivered, i.e. the model of few large ad-agencies which dynamically sell ad-space to affiliates etc.

The usual way adblock-blockers work is by including the ad-content from the same domain as the original page and avoiding URL's and HTML tags/attributes which might be typical for ads. This works mostly, but this way the ad-networks loose a large part of the flexibility (i.e. real time ad bidding). Also users can be tracked less (better for privacgy, worse for ad-networks) and the risk for the user to get infected by malvertisment is much lower.

The other way is to detect ad-blocking (i.e. detect if ads are loaded or not) and simply deny users access to the page if they have ad-blocking enabled. And to make sure that users don't work around outlaw bypassing the ad-block detection by using DMCA or similar laws. See Axel Springer bans adblock users from Bild online for a recent case.

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Ignoring all theoretical and practical considerations, consider the psychology: Adblockers are used by people who don't want to see ads. What do you achieve if you get your ads seen on a computer despite the adblocker? Your ad will be seen by a person who most definitely doesn't want to see it. That person will not start buying the advertised product, instead they will be mightily pissed off and do everything in their power to keep all their friends and family from buying your product.

And then there is the small question of legality. By circumventing measures that I have taken to not display ads, you are hacking into my computer. Some people will take that seriously, will complain at the right place, and get you a substantial fine.

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