auto adding of hosts to table

[Aaron Martinez]

I run some services on non-standard ports and want to deal appropriately 
with people trying to connect to the standard ports. I read somewhere 
(unfortunately i can't find it now) that much like the 'overload' tool 
in pf that you can also dynamically add ip's to a table for connecting 
to a preset port.

For instance, i don't run telnetd anywhere and so if a connection to 
port 23 is made, i would like to add the connecting machine's IP to a 
'bad_guys' table on the fly so subsequent connects will be dropped.  For 
the life of me i can't find where i read this.. is it possible or was i 
imagining it?

Thanks in advance,

Aaron