The network is the hacker's way into your system. If your network is not securely configured, a hacker can move freely between the systems on your network and find weaknesses in other aspects of your security. Good network security is the first (but not the only) line of defense you have against outsiders breaking into your systems. The following procedures will harden your system against a network hacker: Turn off the following services if they are not needed: FTP, RAS, IP Forwarding, and GOPHER. Disable protocols that are not needed, including TCP/IP, NetBIOS, and NetBEUI. Disable Server, Alerter, and Messenger services. Block RPC port 135 at your firewall. Block nbname port 137 at your firewall. Block nbdatagram port 138 at your firewall. Block nbsession port 139 at your firewall.