Forum Moderators: phranque
I installed firewall but that makes my internet conexion slow
If you're on a broadbad connection, then a firewall is an absolute must (along with a properly-updated antivirus, but you knew that already).
You are right in saying that software firewall programs slow down things, so it is best to go for a hardware device such as a NAT router - even the most basic model will give excellent protection. A router with an integrated firewall is even better, and still incredibly cheap - and it allows you to easily share a connection too.
Another nice thing about the *nix setup is that you can run your own DNS servers and, with the right HOSTS file, block a great deal of ad servers on the Internet.