The /etc/securetty file lists the devices on which "root" may
log in. If you remove all entries except for tty1 through tty8,
you'll prevent network logins for root.
ttyS* are serial devices (e.g., a modem or serial-connected
ttyp*, ttyq*, etc are network terminals
Can't telnet as 'root' into the system
You can login as root from the local console, also can do a "su",
but not telnet as 'root'? This is because this is the default
behaviour for security reasons. If you can, use ssh and scp
instead of telnet and ftp. If you cannot or think that your
system is secure, add the necessary number of pseudo terminals
in /etc/securetty. You may also face this problem while logging
from xterms locally.
ttyp0, ttyp1, ...., ttypa, ... (add one in