The problem is that the Ip the files come from must not come from a kidporn swapper but also from people who got those files unwanted like me. The problem is that these files not only got kidporn keywords but also "usual" adult-related keywords and can be downloaded by mistake.

And the interisting/bad thing:
I found out how to check if i got those files on my HD. It seems like that kind of files are preferred from others. So I only have to check what files are uploaded to others. In most cases: kidporn