The changes in the copyright law in September of this year have left the account holder responsible for all the infringing file sharing activity that happens on their account. But how can you tell what sort of activity has been registered to you?

Well if you have access to the logs on your servers you can pour through them and compile a list of likely traffic sources....or you can visit youhavedownloaded.com. 

By entering your account IP address (visit http://whatismyipaddress.com/ from a computer on your network to find this) the website will give you a list of any torrent files that have been recorded as having been downloaded on your account.

Interesting reading.