Glossary definition: Zero Day

Zero Day: A Cybersecurity Threat

Zero Day: A zero-day (also known as a zero-hour or zero-minute) vulnerability is a computer security vulnerability that is unknown to those who would be interested in mitigating the vulnerability (including the vendor of the target system). It is usually discovered by an independent security researcher or hacker and then made public, sometimes with working exploits. These vulnerabilities are extremely dangerous because they can be used by malicious actors to gain unauthorized access to a system or network, allowing them to steal data, install malware, or even take control of the system. Zero-day vulnerabilities are difficult to protect against because they are unknown to the target system's vendor, leaving the system vulnerable until a patch is released.