Ralph’s been a good employee for you. Shows up on time. Gets the job done. Doesn’t hassle anybody. He’s also a porn addict. When nobody’s looking, he’s visiting sites – on your network – that you’d be appalled to see.

You stride into the office early one Monday morning. You grab a cup of coffee, flip on your computer and start checking e-mail… A note pops up that rivets your attention: “Your files have been encrypted.