If you get up from your computer, lock it!
"I sent an email to your boss letting him know what you really think of him". This Notepad message was on my screen when I got back to my cubicle after getting up to stretch my legs. What? I had been gone for 180 seconds -- three quick minutes. Lucky for me, the note turned out to be from our systems administrator who wanted to make a point. All it takes is about one minute for a disgruntled colleague to send a message on your behalf to the boss and there is no way for you to prove you didn't send it. In about 30 seconds, a cracker could install a keystroke logger to capture everything you type including company secrets, user names and passwords. In about 15 seconds, a passerby could delete all your documents.