Hi,
Nokia's Internet tablets are pretty secure out of the box, ports are well closed, but a small firewall never hurts. Alas, I have not found one (so far). So here is a small hack:

open an editor and create a file with this inside:

#!/bin/sh
iptables -F
iptables -A INPUT -p all -s 127.0.0.1 -j ACCEPT
iptables -A INPUT -p tcp --syn -j DROP

save it, and make it executable (chmod +x). Then, run it as root.

You will have a very basic, but solid, firewall.

HTH,

VS