What is Zero-Day?

A software vulnerability that is unknown to the vendor and has no official patch or fix available.

Expanded Explanation

A zero-day vulnerability is a critical security flaw that is discovered and sometimes exploited by attackers before the software developer is aware of it. Because there is no fix or patch at the time of discovery, zero-day attacks can be extremely damaging and difficult to defend against. These vulnerabilities are highly prized on dark web markets and are often used in advanced persistent threats (APTs).

Related Terms

Exploit, Vulnerability, Patch Management, Threat Intelligence, APT

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