Hacker Culture A to Z

Chapter 26. Z

Zero day

In cybersecurity, a zero-day vulnerability is a security vulnerability in a software or hardware product that exists for some time without the knowledge of the product’s vendor (such as Microsoft for Windows, or Samsung for Galaxy Android phones) or the cybersecurity community. MITRE’s Common Vulnerabilities and Exposures (CVE) database is a good way to check whether or not a vulnerability is a zero day.

A zero-day exploit is a cyberattack method of which the vendor and the cybersecurity community were previously unaware.

Nothing bad has to happen for zero-day vulnerabilities and exploits to be discovered. Sometimes penetration testers and bug bounty hunters find them before an attacker does. Other times, zero-day vulnerabilities and exploits are discovered after a zero-day attack, when a threat actor exploits a previously unknown vulnerability or uses a previously unknown exploitation technique in a successful cyberattack.

See also “Common Vulnerabilities and Exposures (CVE)”, “Cybersecurity”, “Exploit”, “Penetration testing”, “Stuxnet”, “Threat actor”, “Worm”

Zettabyte Era

A zettabyte is a very large amount of computer data: about a thousand exabytes, a million petabytes, or a billion terabytes. To put that in perspective, a really good solid-state drive in a laptop in 2023 might have about 1 terabyte, and a good external hard drive around 4 terabytes.

In 2012, global internet traffic hit a milestone: it went past 1 zettabyte. In 2016, the amount of ...