A number of xinetd services send messages in clear text. In Chapter 22, you’ve seen how this can put even your passwords at risk. One alternative for remote access to a Linux computer is the Secure Shell (SSH). The SSH daemon can be configured with private and public keys to encrypt messages over a network.
With all of these levels of security, it isn’t always easy to diagnose a service problem. If users are having trouble accessing a server, you may need to check the available firewalls, one at a time. Other possibilities are that services are not active, or that various iptables commands or TCP Wrappers are blocking access.