I know you have to be careful when downloading or installing thing from the internet in order to protect yourself from malware but occasionally I'll get it installed without downloading anything. I'll just be browsing when suddenly my browser crashes and when I bring it back up lo and behold I have a new homepage. How does this happen and how do I prevent it in the future?
Windows Vista Home Basic
Firefox (Though I don't ever remember being on anything but Chrome when it happens)