freebsd-pf Stealth Modus

[Nico De Dobbeleer]

Hello, 

I just finished installing FreeBSD 7.x with pf in transparant bridging mode as the servers behind the firewall need to have an public ipaddress. 
Now is everything working fine and the FW is doing his job as it should be. When I nmap the FW I see the open ports and closed ports. 
Is there a way the get the FW running in stealth mode so that isn't possible anymore with nmap or any other scanning tool to see the open or closed ports? 

When I look around I hear roomers that there's something like blackhole that can be added in the sysctl. 

Anyone an idea? 

Kind regards, 
Nico