Red Hat Linux 6.2: The Official Red Hat Linux Reference Guide
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# Controlling Access to Services

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:

    ALL: redhat.com .redhat.com
    in.talkd: ALL
    in.ntalkd: ALL
    in.fingerd: ALL
    in.ftpd: ALL

This configuration allows all connections from redhat.com and `*.redhat.com` machines. It also allows talk, finger, and FTP requests from all machines.

tcpd allows much more sophisticated access control, using a combination of `/etc/hosts.allow` and `/etc/hosts.deny`. Read the tcpd(8) and hosts_access(5) man pages for complete details.

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