Zero day意思

"Zero-day" is a term used in the context of cybersecurity to describe a vulnerability in a software, system, or device that is unknown to the vendor or developer and, therefore, has not been patched or fixed. A zero-day vulnerability is particularly dangerous because it can be exploited by attackers before any security measures can be taken to protect against it.

Once a vulnerability becomes known to the public, developers typically have a "window of exposure" to fix the issue before attackers can exploit it. During this time, the vulnerability is said to be in the "zero-day" phase, meaning that it has been publicly disclosed but no patch or fix is available yet.

A "zero-day exploit" refers to the use of a zero-day vulnerability to launch an attack. Once a patch is released by the vendor, the vulnerability is no longer considered a zero-day, as it is now known and a fix is available.

The term "zero-day" comes from the idea that the vendor or developer has "zero days" to fix the issue before it can be exploited. It is a highly sought-after and valuable commodity for hackers and cybercriminals, as it allows them to launch attacks that are difficult to defend against.