The most dangerous cyber threats are the ones we don’t know about yet. Most cyber defenses rely on already knowing what the attack looks like. This is why zero days are so dangerous: we simply don’t know what they are.
A zero-day attack occurs when hackers exploit a software or hardware vulnerability that is completely unknown to developers and the wider cybersecurity community. Because no one is aware of the flaw, no defense has been developed against it, leaving systems vulnerable. This means that even if you're using top-of-the -line cybersecurity software, like the best VPN or best antivirus, you could still be vulnerable to zero-day attacks. The term "zero-day" refers to the fact that security teams have had zero days to fix or patch the vulnerability.
