> Sorry, i am using ipnat. The two major domains i'd like to allow ftp to
> my machine are earthlink.net and woh.rr.com everything else should get an
> rst response.
You'll have to look up the the net blocks for those domains, and
use rules something like
block in return-rst on <interface> proto tcp from any to <address> \
flags S/SA
block in on <interface> proto tcp from any to any
pass in on <interface> proto tcp from <net block> to <address> \
port = 21 flags S/SA keep state
(There are lots ways to write rules achieving the same effect.)
Note that giving the "earthlink.net" domain access to your FTP
port allows connections (and port scans) from, oh, several hundred
thousand addresses.
> Is there other techniques i can employ to negate the effect of a
> portscan?
Don't sweat port scans. If your system is secure, they can't hurt you.
(In other words, don't rely on packet filtering alone for network
security. Make sure the software you use for any network services
has no known vulnerabilities, and that it's configured properly.)
David S.
