blackhole in PF possible?

[Ighighi Ighighi]

blackhole(4) is hardly a feature if it applies to loopback interfaces
as well.  Its intended functionality
("to slow down anyone who is port scanning a system", according to the
manpage) also slows down
internal services because those TCP RST's and ICMP Port Unreachable's
are never seen.

Is there a way to get the same functionality in PF so I can restrict
those packets to external interfaces ?

Thanks in advance,
Igh.