A high-speed internet connection can make your computer more vulnerable to spyware, slowing your performance by up to 500%.Say what? If spyware slowed your computer down by 100%, it would be completely frozen. So if it's been slowed down 500%, is it going backwards?
I assume this is yet another example of the base-switching problem. I'm guessing the reality is that spyware can slow your computer by about 84%. Rather than using the original performance level (100% of top speed) as the base for calculating the percent change, they used final performance level (16% of top speed) instead. This yielded a percent change of over 500% (going from 16 to 100), which they erroneously called the percent decrease.
But I'll admit there could be some computer jargon here that I don't get.