screaming tty n.
[Unix] A terminal line which spews an infinite number of
random characters at the operating system. This can happen if the
terminal is either disconnected or connected to a powered-off
terminal but still enabled for login; misconfiguration,
misimplementation, or simple bad luck can start such a terminal
screaming. A screaming tty or two can seriously degrade the
performance of a vanilla Unix system; the arriving "characters"
are treated as userid/password pairs and tested as such. The Unix
password encryption algorithm is designed to be computationally
intensive in order to foil brute-force crack attacks, so although
none of the logins succeeds; the overhead of rejecting them all
can be substantial.