What are zero-day vulnerabilities?

What happens when hackers find vulnerabilities before developers?

Features By Sam Dawson published 29 September 2024

Even if you aren't up to date on the latest cybersecurity happenings, you're aware that there are plenty of threats lurking on the internet. Whether it's scam emails, hackers stealing your personal info from websites, or malware spying on your computer, there's a lot to be on the lookout for. The good news is that these threats are relatively easy to spot and counter.

That's not so true for zero-day vulnerabilities. They're a class of hacking attacks that are completely unknown at the point they're deployed. You probably won't run into one while you're browsing the internet, but they're one of the biggest threats that companies face online.

Stick with me and I'll explain what zero-day vulnerabilities are, how they occur, and why it's nearly impossible to stamp them out.

What are zero-day vulnerabilities? 

A zero-day vulnerability is a flaw in how a software or hardware system has been built that the developers aren't aware of. By definition, it's impossible to know how many zero-day vulnerabilities there are in a system.

These vulnerabilities can be used by a malicious actor to cause the system to do something unintentional. Perhaps it allows a hacker to grind a network service to a halt, making it unusable for anyone else. Maybe there's a flaw in how the authentication works that allows a hacker to get into a company's data stores without the correct password.

It could be absolutely anything, but the one thing all zero-day vulnerabilities have in common is that they're new. The term "Zero-day" itself refers to the amount of time the developer has had to respond to and fix the vulnerability.

If you were to think of network security as trying to secure a house, the zero-day vulnerability is like a window you don't know can be opened from the outside.

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