Denying connections

[Me! <oli@xxxxxxxxxxxxxxxxxx>]

Hi,
I wasn't sure if this is more of a Linux question than an ircd Q, so I decided
to take my chances...
There is a domain that I want to deny access to all the ports that ircd runs on,
the reason for this is simple, there is someone there that keeps sending clones
to the server without delaying and the server gets slow when it has to deny that
many clients so fast(I am upgrading the hw in a few day's, so it might get better)
and I would like to deny all connections from that host without ircd ever knowing
that the connection attempt was made.
Does anyone have an idea on how I can do this?

				Oli

P.S. I'm running a RH4.2