to do this "legally" dont u need "good reasons " for doing it? and this site is very clear on "illegal activity" and the non-promoting of same:)
we have our on-line activity scrutinised by the Admin , and we see, at long on, a screan warning us of such ; are u suspicious that someone is abusing something? and have u sent an e mail to all your employees (or contacts over which u have "juristiction ) advising them of "proper conduct" while on work PC"s?
I recall a thread on a similar "vein" a long while back ; I think you may have to install a particular program on your PC that "monitors" where other users are going and what doing ;can you give your OS etc please for the experts to give a stab at this? If I can find the other thread I"ll post a link for you.
Our computers at work are closely scrutinized for all sites we visit, and a warning has only recently been given that some people have intentionally been "misusing " hospital property by visiting "inappropriate sites" , and that they face dismissal for knowingly so doing:(