demon dialer
n.
A program which repeatedly calls the same telephone number. Demon
dialing may be benign (as when a number of communications programs
contend for legitimate access to a {BBS} line) or malign (that is,
used as a prank or denial-of-service attack). This term dates from the
{blue box} days of the 1970s and early 1980s and is now
semi-obsolescent among {phreaker}s; see {war dialer} for its
contemporary progeny.