Some larger systems keep a dedicated number for the after-hours modem line, usually different than the normal modem line numbers. How a Modem Handles a Call For a user to gain access to Linux through a modem line, the system must use the getty process. The getty process itself is spawned by the init process for each serial line. Some Linux systems allow a dialup password system to be implemented. This kind of system 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 used by the user.
You can apply the same procedure to UUCP access. Although this program was designed with good security in mind, it was designed many years ago and security requirements have changed a lot 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. Remote systems dialing in using UUCP log in to the local system by supplying the uucp login name and password.