A zero-day exploit is when hackers take advantage of a software security flaw to perform a cyberattack. And that security flaw is only known to hackers, meaning. Software developers have no clue about its existence and have no patch to fix it. This is why, when a zero-day attack is detected, it needs to be mitigated immediately. In other words, there are “zero days” to fix vulnerability because it’s already been exploited. Here, we’re zeroing in on the zero-day concept, including just what is a zero-day exploit, and how to avoid them. 1. Zero-day definitions: What is zero-day? The term “zero-day” refers to a newly discovered software vulnerability and the fact that developers have zero days to fix the problem because it has been — and has the potential to be — exploited by hackers. Sometimes written as 0-day, zero-day definitions run the gamut: A zero-day vulnerability , also known as a zero-day threat, is a fla...