#1. Do most crackers use dos, linux or unix (or something unmentioned) when they are cracking a server or a computer?

#2. I have recently read an article in the recent wired (dont ask me which one though) about a guy who hacks into servers and other computer systems using only a browser. How is this possible? And if you can do it using just a broswer, than why arent so many crackers hacking using it?