What Is a Zero-Day Vulnerability and Why It's Dangerous222

A zero-day vulnerability is a flaw that's exploited before the vendor has a chance to patch it — hence "zero days" of warning.

Why it matters

Signature-based detection can't catch what it's never seen. That's why behavioral and heuristic detection matter so much in our protection scoring.

What you can do

Keep software updated, and choose a security suite with strong behavioral detection — check the Protection Rate section on any of our reviews.