Zero-Day

A zero-day is a software security vulnerability the vendor doesn't yet know about, so there's no patch for it — they have "zero days" to react. If attackers discover such a flaw first, they can exploit ✕ An exploit is code that specifically takes advantage of a security flaw to break into a system or plant malware. More in the glossary → it with no protection in place; these "zero-day exploits" are especially dangerous and sought-after. Fast updates (as soon as a patch arrives) and security programs with behavior-based detection — which can stop unknown attacks too — help. More in the best antivirus comparison.