"A zero-day (or zero-hour or day zero) attack or threat is an attack that exploits a previously unknown vulnerability in a computer application, meaning that th

"A zero-day (or zero-hour or day zero) attack or threat is an attack that exploits a previously unknown vulnerability in a computer application, meaning that the attack occurs on "day zero" of awareness of the vulnerability." [1] If the party responsible for fixing a vulnerability knows of it before it is exploited, then they had more than "zero days" to fix it. [1] http://en.wikipedia.org/wiki/Zero-day_attack http://en.wikipedia.org/wiki/Zero-day_attack