Files that specify TCP/IP access permissions:
1) .rhosts - set up by each user under their home directory to specify who can remotely access their account. Not a very secure way of doing things.
2) /etc/hosts.allow - checked by the system for hosts that are allowed connections.
3) /etc/hosts.deny - checked by the system if the host was not found in /etc/hosts.allow. Specifies hosts that are to be refused connections.
4) /etc/hosts.equiv - used to grant certain hosts and users access to accounts on your machine without having to supply a password. This is a security hazard unless you control access to all the machines listed in this file. Your machine is only as secure as the least secure of the "trusted" hosts listed in this file. If you care about computer security, you should not use this file. Users should be discouraged from using the .rhosts file as well. You are better off using ssh (secure shell).
(5) /etc/inetd.conf - used to disable unwanted tcp/ip services. After modifying the configuration file you will have to restart the inetd
daemon. The simplest way to do it on Linux is to send a hang up signal to the
daemon which will force it to re-read its configuration file:
killall -HUP inetd
The hosts_access(5) man page provides information on the syntax /etc/hosts.allow and /etc/hosts.deny.
Sometimes you should use the hostname inclusive domainname.
Regs David