There are only so many ways that a computer security ad can beat you over the head with the message that you should be using anti-virus software. However, this one from Ziggo is a brilliant way to demonstrate the need.
A guy is shown working away on his laptop in a public place, when a dancer in hot pants gets up onto the table and makes her presence very known. The woman is tempting, just like something a little suspect that you might want to download or click on. However, in a matter of seconds, she draws a curtain and she's gone. A few beats later, she's miraculously appearing on the screen of the guy's laptop. It looks like it's all staged, but if it's not, it's some pretty good magic.