Zero-day refers to newly discovered vulnerabilities that allow hackers to attack systems before developers can fix them. The term originates from internet piracy, where it describes illegal releases on the day of publication. A zero-day attack occurs when attackers exploit the vulnerability before developers fix it.
The term refers to the amount of time developers have to close the vulnerability. Once a patch is available, the vulnerability is no longer considered a zero day. However, systems remain vulnerable if admins and users do not install the latest updates, often leading to critical data breaches.
In the field of cybersecurity, zero day refers to a vulnerability that is exploited by attackers before the provider becomes aware of it. The clock is ticking for the provider as soon as the attack technology is offered for sale on the dark web.