The Intertubes are ripe with evil. You can smell it. Crouching there, in the dark recesses of zeroes and ones, waiting for a fresh unpatched computer to poke its nubile head out into the word. Bang! Another poor netizen gets 'sploited, turning it into a zombie, or worse - his data is entirely compromised, and somebody's buying a new TV with your credit card… bad... To protect yourself, you download the latest updates, install anti-virus software and even have software firewalls installed. Even then, software is, by design, soft and once an exploit is found, it can be modified and worked around, and you're vulnerable again. It's almost impossible to keep up.
Yoggie Gatekeeper Pro