Today, I found out that some images are not shown on the home of Blocks4.NET for those who have Kaspersky installed and anti-banner feature activated. The good news for those who use this feature is that the images are indeed banners. :)

The interesting fact is that the banners are not served by a third party, are just images from our server. So, how Kaspersky knows these images are banners? (No need to say the other images are loading just fine)

Here is what Kaspersky say about their module (version 6.0):

 Anti-Banner, a module in the Anti-Spy component that blocks advertising content on web pages, previously detected such content only based on lists updated from Kaspersky Lab websites or manually defined by the user. A heuristic analyzer has been added in the Anti-Banner module in MP1. Now the module can detect banners that are not listed, so more advertising banners are blocked

So, an heuristic analyzer has been added ... 

The answer to our problem was suggested by Nicolas Cadilhac from VisualHint. He observed that the url path for the images contained "\ads\".  Probably the heuristic analyzer is also searching the url paths for common words like ""ad", "ads", etc. After replacing "ads" from the url paths, the banner images were shown.

I have tested using Kaspersky Internet Security 6.0, which is, by the way, a great tool.