It surprises me that nobody has still recalled the spectacular bug from 1990, which inspired an historical witch hunt against the hacker community, as well as the book by Bruce Sterling, which tells about all of that (The Hacker Crackdown, see external links for getting a legitimate copy of it).

The following are excerpts from the book.

On January 15, 1990, AT&T's long-distance telephone switching system crashed. This was a strange, dire, huge event. Sixty thousand people lost their telephone service completely. During the nine long hours of frantic effort that it took to restore service, some seventy million telephone calls went uncompleted.
...
An obscure software fault in an aging switching system in New York was to lead to a chain reaction of legal and constitutional trouble all across the country.
...
Telco officials wanted to punish the phone-phreak underground, in as public and exemplary a manner as possible.
...
Unfortunately, while it was busy bookkeeping with the status map, the tiny flaw in the brand-new software came into play. The flaw caused the 4ESS switch to interact, subtly but drastically, with incoming telephone calls from human users. If—and only if—two incoming phone-calls happened to hit the switch within a hundredth of a second, then a small patch of data would be garbled by the flaw. But the switch had been programmed to monitor itself constantly for any possible damage to its data. When the switch perceived that its data had been somehow garbled, then it too would go down, for swift repairs to its software. It would signal its fellow switches not to send any more work. It would go into the fault-recovery mode for four to six seconds. And then the switch would be fine again, and would send out its "OK, ready for work" signal [...] As soon as they stopped to make the bookkeeping note that their fellow switch was "OK," then they too would become vulnerable to the slight chance that two phone-calls would hit them within a hundredth of a second.
...
As it happened, the problem itself—the problem per se—took this form. A piece of telco software had been written in C language, a standard language of the telco field. Within the C software was a long "do ... while" construct. The "do ... while" construct contained a "switch" statement. The "switch" statement contained an "if" clause. The "if" clause contained a "break." The "break" was SUPPOSED to "break" the "if clause." Instead, the "break" broke the "switch" statement.