As a security measure, most network services are managed by a
protective program called a TCP wrapper. The protected
services are those listed in /etc/inetd.conf that specify
/usr/sbin/tcpd. tcpd can allow or deny access to a service
based on the origin of the request, and the configuration in
/etc/hosts.allow and /etc/hosts.deny.
By default Red Hat Linux allows all service requests. To disable
or limit services you can edit /etc/hosts.allow. Here is an example
/etc/hosts.allow file: