Can't upvote this enough. It's very hard to stop a determined attacker, but that's not what this is covering. As a developer sometime I peer program, and that

Can't upvote this enough. It's very hard to stop a determined attacker, but that's not what this is covering. As a developer sometime I peer program, and that might mean handing over the controls to a colleague. Now I trust my colleagues, but you never know what their personal lives might me. If I had, say, saved my internet banking password (I don't, but let's entertain the possibility) they could easily access the password list and copy it, then close it without me ever knowing. It's much like leaving an open safe under my desk. Even if it's a simple lock people won't open it to see what's there. If you know I have a stack of gold you might decide to break in, but you'll know it's wrong.