What is a zero-day?

The term “zero-day” refers to a new, previously unknown vulnerability in a computer system or program. This flaw can be caused by a bug, a system glitch or a design error.

The name “zero-day” comes from the fact that no patch yet exists to mitigate the vulnerability being exploited, as neither the product manufacturer nor the security community are aware of its existence.

Although a zero-day vulnerability can be discovered by accident, they’re typically found by expert hackers seeking to find, exploit and monetize them.

When a zero-day vulnerability hasn’t been identified or patched before a criminal finds and starts using it, it becomes a zero-day exploit or zero-day attack.