If someone sends you an Email with an attached virus designed to hack into your computer and send information to a remote computer, that's illegal.
If someone breaks into your home and installs a keystroke logger into your keyboard, that's illegal.
If someone parks outside your home and hacks in to your wireless network, that's illegal.
Unless it's the police doing it. Then it's all okay.
Nothing to worry about. It's regulated by RIPA so it'll never be abused. Okay, you can laugh now. When you've finished, strengthen your firewall, replace your wireless network with a wired one and get a second USB keyboard - which you take from its hiding place, plug in and use instead of the one that's permanently connected to your computer.
But we're not a police state. Oooooh, no.