I reckon the only answer is to follow the advice that good old Richard from Naples gave someone here recently. Use a good firewall, stay away from dodgy sites, don't open unsolicited e-mails and reformat your hard drive every few weeks, then reload all your software. It only takes a couple of hours and the machine works really fast afterwards.
We must lobby for the death penalty for intruders. More sensibly though, we need to unmask those companies that pay for intruder services and blacklist them for our purchases. RealPlayer for starters, and no, I don't want a Rolex watch, painkillers, porn, mortgage advice or a loan.