Problems with Application Server and Netscape Web Server

It seems that somebody is trying to hack the machines in my job. They are two Unix boxes, the first, a SunSparc4 that runs Application Server, and the second, an IBM AIX that runs Oracle7.3 and Netscape Server.

The fact is that, at the time that App.Server starts, somebody sents a huge number of request that becomes the performance of the Oracle Server very very low, even null.

My question is: Is there any form to limit the CPU use for Netscape+App Server, or limit the number of request, or close the web port for an specific IP address (the place where the attacks come from)

Thanks for your answer and regards from Chile

-- 
Atte.
Álvaro Palma Aste
Grupo de Ing Biomédica - U. de Chile
apalma_at_cipres.cec.uchile.cl