Find the definition of the most commonly used cyber security terms in our glossary below.

What is Blacklisting in cyber security?

Blacklisting, the exact opposite of whitelisting, involves creating a list of known malicious entities, like IP addresses, URLs, applications, or email addresses, which are blocked or denied access to a system. Unlike whitelisting, a blacklist will block only specific entities on the list instead of blocking everything by default. It's typically used to prevent access to malicious websites, block spam emails, and stop potentially harmful applications from running. While blacklisting can be effective at mitigating threats, it can lead to false positives, and it’s reactive, needing constant updates as new threats emerge.