[link|http://www.redhat.com/docs/manuals/linux/RHL-9-Manual/ref-guide/ch-tcpwrappers.html|http://www.redhat.co...-tcpwrappers.html] redhat description
basically it is an ACL based on ip inbound packets

tcp_allow
drewk's work site
folkert to fix things

tcp_deny
anyone else

if the packet is on the allowed list then the inbound service is called, in this case sshd to service ssh requests.
thanx,
bill