The infamous Morris Worm was released in 1988; making use of known
vulnerabilities in Sendmail/finger/RSH (and weak passwords), it took out a
metric shitload of SUN-3s and 4BSD Vaxen (the author claimed that it was
accidental, but the idiot hadn't tested it on an isolated network first). A
temporary "condom" was discovered by Rich Kulawiec with "mkdir /tmp/sh".
Another fix was to move the C compiler elsewhere.