1. Zero-day definitions:

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 flaw in security software that’s unknown to someone interested in mitigating the flaw, like a developer. A zero-day exploit is when hackers take advantage of a zero-day vulnerability for malicious reasons, oftentimes by way of malware to commit a cyberattack.