Cleener.org

A filter to stop your staff or pupils from downloading things they shouldn't, that is, copyright files that have been pirated.

Boo, hiss. Spoilsports.

It works by reading a database of naughty URLs, and that's all they're saying about that. No clues as to how they choose. But the code that reads it and returns the results is there on the page and it's free, so anyone with PHP programming skills can grab it and insert it into their own applications.

If you have concerns or delusions that your staff are downloading pirated materials in the background whilst pretending to do the accounts or that your pupils are oddly more interested in their online studies than they ought to be, this may be for you. And it has an advantage over the more common method of banning URLs because it only prevents the download of certain files from a host, and not others.

The site itself is about as basic and unrevealing as it could be. Understandably, they're not telling everyone how they're discerning between the legitimate and pirate materials, so you'll need to email them to find out more.

I always assumed that everything on file-sharing sites was pirated, one way or another, so it's a surprise to me that there are still legitimate files up there at all. I'll have to take their word for it.