Detecting AdBlocking software?

All off the methods mentioned here rely on the ad blockers to strip out code. This doesn't work for some adblockers(like NetBarrier on Mac). You also have to keep updating your code when the adblockers catch on.

To detect if the user is blocking ads, all you have to do is find a function in the ad javascript and try testing for it. It doesn't matter what method they're using to block the ad. Here's what it looks like for Google Adsense ads:

if(typeof(window.google_render_ad)=="undefined") 
{ 
    //They're blocking ads, do something else.
}

This method is outlined here: http://www.metamorphosite.com/detect-web-popup-blocker-software-adblock-spam

This is something that simply can't be done server side - there's zilch reason for person to knock on your door and say "Look at me, I have AdblockPlus!". When on the client side, adblock is actively trying to influence the page content, which is something you can see happen and see that they are using an adblocker.

Anyway, I happened to know that newgrounds.com is doing this too. (their new layout was screwed up for adblock plus users - as a response they made a contest for the best "if you're not going to help us through our ads, go and buy something in the store"-banner.

A quick look in the source of newgrounds told me they are doing this with some simple javascript. First in the document:

var user_is_leecher = true;

Next there is a external script tag: src=checkabp?thisistotrickabp=***adress of ad affilliate***

Now the joke: they simply trust adblock plus to filter that script out, as all that's in there is: user_is_leecher = false;

From there, they can do just about anything.