Q: prevent malware, hijacked browser, and popups?

Hello,

What is the best way to prevent browser hijacks, malware, and pop-ups? I am in a wide open connection without firewall. Also how does one quit the browser when there's a dialog box open? (I don't dare touch those when they pop up as I feel that's part of their process to infect my computer)

command quit does not work.

Thank you!

- Judy