you could use IPTRAF search the forums, has been posted many times or go over to
http://contribs.org.
Or you could use squidguard at end of night will give you a report of which IP number has visted any URL and how many time, for how long and how much has been downloaded from that IP address.
Again search the forums or take alook at contribs.org
Sorry but I couldnt rember where I downloaded from.
Hope this helps
Byte