Some larger systems keep a dedicated number for the after-hours modem line, usually different from the normal modem line numbers. In order for a user to gain access to Linux through a modem line, the system uses the getty process. The getty process itself is spawned by the init process for each serial line. Some Linux systems enable a dialup password system to be implemented. This forces a user calling on a modem to enter a second password that validates access through the modem.
Access is determined by the type of shell utilized by the user.
The same procedure can be applied to UUCP access. The UUCP program was designed with good security in mind. However, it was designed many years ago, and security requirements have changed considerably since then. A number of security problems have been found over the years with UUCP, many of which have been addressed with changes and patches to the system. Still, UUCP requires some system administration attention to ensure that it is working properly and securely.