I'm well aware of it. This goes one step further though, and from my reading of the document it would require a hash of every document you retrieved to be compared against a table of 'illegal' files.
The problem is you can trivially change a files hash in about 2 minutes using paint.
So filtering like that is basically pointless.
However.
I don't see any of this in that report linked to (it's early :P). Where am I reading about filtering? (page?)
It's late, not early. Need to get some sleep...
EDIT: actually, somewhat ironically, CIRCAMP is one of the few EU organisations that "gets" the child porn problem properly.... I hear they actually have had success going after distributors. More on them here: http://circamp.eu/index.php?option=com_content&view=arti... (I think the use of the word filter in the report was just a poor choice of words - it refers to CSAADF, the blocklist)