spying

So I hate the idea of logging someone's net usage as much as the next guy, but since i's my job ...

I've got a user here that I need to log. pretty sure she's clearing out her internet history when she closes firefox. The machine is running ubuntu. I basically just need a list of fires she visits over the course of the day for review.

Anyone? i can't grab it on the firewall, because it's ltsp and she doesn't have her own ip address, but I do administer the ubuntu box that ltsp is running on.