As of version 1.27, the login program recognizes the file

	/etc/usertty

where one, for certain users, can specify which tty's they are allowed
to login on. This can be beneficial if for example, you have a number of
users logging in via modem only. Should one of their passwords be 
known in the hacker community, the hackers will only be able to attack
your machine via modem, and not via the net.

Also, restricting modem log-in ability to those (few) who have a 
legitimate need may prove a good idea. Hackers with a stolen password
will often attack a machine via modem in order to hide their true
identity, so limiting the number of accounts permitting modem login
limits the chances that such an attack will work.

You may also want to restrict access via a high speed modem to 
a chosen few, and forcing others to use a slower line.

Each line in the /etc/usertty file has the following format:

<username>	<tty1> <tty2>...

Comments start with a # and extend to the end of the line.

The <username> should match the username in the passwd file. The <ttyn>
names should the the filenames of the device files with the leading
path deleted. Here's an example file:

---------------------------
# /etc/usertty, for certain users, allow login
# only on certain tty's
root	tty1
brian	PTY tty1 tty2
stduser	tty1 tty2 ttyS0
---------------------------

This file will only permit stduser to log in on tty1, tty2, and ttyS0 (ie.
/dev/tty1 and so on). Users not mentioned in the file are by default
allowed access to all tty's.

PTY is an alias for all pseudo tty's, ie. ttyp0, ttyp1,...

It might be a good idea to restrict root-logins to the console. But
be careful not to lock yourself or root out!

If the file does not exist, all users are allowed login on all tty's, ie.
good old standard behaviour.
