I've got a web application which can be used for individual peoples (one account for one person) and for places such as schools (one account per computer). I would like to make sure that the schools accounts can only be logged in from the said school.
I've tried an IP filter which isn't appropriate as they have a dynamic IP (it changes every day or each time they reboot their ISP box). The MAC address is not an option since it's not readable by PHP and not conserved between packets hops.
So here is my question, how may I make sure that the schools accounts are used from and only from the school ? Maybe something that I have to install on each trusted computer and which can't be cleaned without paying attention ?