when scanning open ports I noticed UDP ports 135, 137, 138, 139 (netbios) and 1080 (IRC) have all be left open. Is this something I should worry about?
Depends. If you are not running Samba, then there is no reason to have the netbios ports open at all. If you are running Samba, then those ports should be open only to the neccessary hosts on your network. Either way, the Samba ports should not be open to the internet in general (Samba isn't really designed as a security hardened server application). If your are not running an IRC server, then you should not have that port open either.
In general, to close a udp port:
iptables -I INPUT -p udp --dport
<port_number> -j DROP
So to close udp port 135:
iptables -I INPUT -p udp --dport 135 -j DROP
Just goes to show you that a large firewall script does not equal a good firewall. I've seen plenty of small, concisely written firewall scripts that are very effective. Also I probably wouldn't use stuff from Viginia Tech, you never can trust those Hokies
