A friend of mine who was away for a week has reason to believe that there was unauthorized usage of her computer. A complete clean-up of her history had been conducted but not by her and so I wondered:

1. Is there a way to determine what internet activity had taken place once a clean-up program has been used?

2. Are clean-up programs credible?

3. Is there a way to block sites in general, for example porn sites?

Any extra info about this sort of thing would be appreciated.