Using Firefox is not a pancea as it pertains to keeping bad things from your computer.
If you do not take some time to setup the security, from its defaults, you are choosing to make it easy for bad things to get to your computer.
Nah Yeager. I am online all the time, I do not run a firewall, nor do I use any anti-virus programs, nor any anti-spyware programs. You just have to take some time to configure things properly and be a bit careful about what you click on.
MySpace and Youtoob are two fine examples of good ways to get burned.