I have written my own firewall script, somwhere in the script I call the following line:

iptables -P INPUT DROP

This line causes some issues on my linux machine:
I have no aibiltiy to surf and I can't ping any of my machines on my internal network / hosts on the internet.

Removing this line causes my ports to be in 'closed' in stead of 'stealth' status.

Is there any way get a workaround ? So I'm still at stealth mode, but PING works (at least for my internal network)

With that policy rule, you need to specifically ALLOW each bit of traffic back into the box..

Usually with these 2 rules..

iptables -I INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -I INPUT -m state --state INVALID -j DROP

This -I puts the rule first in the chain, so the effect is the second rule is 1st after it loads.

If you want anything to find ports on your box, you will need to make rules to allow them, otherwise nothing gets through to see you.

Of course, that still depends on the rest of your rules...
What did you use as a reference to build your ruleset?
My favourite is http://iptables-tutorial.frozentux.n...-tutorial.html

best tutorial on iptables.

even official netfilter.org docs can beat it.