Newie questions about security

["Jordi" <acero_64@yahoo.com>]

Hello,

I just managed to configure my server and router and ips yesterday and
now I have questions about security. I did a scan of ports and saw the
only open are the ones I opened. I also set my router firewall to
"standard".

1) Must I CLOSE the ports that I don't use? Or just let them not
forwaded? (they appeared as STEALTH in the ports scan)
2) Should I use an extra firewall in my server plus the one that my
router has ? What about Firestarter? Any other good GPL firewall?
3) Should I adjust the firewall in my router to something custom, not
standard, and what do you recommend me?
4) I fear intruders and specially ddos. I saw a IDS called Snort that
many people use. What do you think? Any other good GPL IDS?
5) Now that I have the server running, y suppose I must stop using
gksudo and use only sudo. Not?

Thanks for your answers.

Jordi