Z

Zero-Day

Zero Day;' refers to the length of time that a hack or vulnerability that is unknown - or in other words, it's time in circulation is 'zero days'. A company such as Google or Apple will check how long a vulnerability is known in the wild - and then count the days until it is fixed. FYI Zero Day vulnerabilities are extremely expensive - so much so that companies will spend a lot of money, time and effort in order to protect against these exploits.