Security and the Systems and remote.unknown files

On most BNU systems, only remote systems listed in the /etc/uucp/Systems file or one of its substitutes (specified in the Sysfiles file) can log in to the local system.

The /usr/sbin/uucp/remote.unknown script is executed whenever an unknown system attempts to call the local system. This script refuses to let the unknown system log in and makes an entry in the /var/spool/uucp/.Admin/Foreign file recording the time of the login attempt.

With root authority, or as a BNU administrator, you can modify the remote.unknown shell procedure to log more information about the remote system or to store the information in a different file. For example, you can modify the shell procedure to send mail to the BNU administrator whenever an unknown system tries to log in.

By taking away execute permissions on the remote.unknown shell procedure, you enable unknown machines to log in. In this case, you should add a MACHINE=OTHER entry to the /etc/uucp/Permissions file to establish permissions for the unknown machines.

Your system can contact only remote systems listed in the Systems file. This prevents users on your system from contacting unknown systems.