What is a Blacklist? Definition, Purpose, and Examples

A blacklist is a list of entities that are prohibited or blocked from accessing certain resources or services. In the context of computer security, a blacklist may be used to block malicious software (malware) or other unwanted programs from running on a system.

For example, a firewall might have a blacklist of known malware signatures that it checks against incoming network traffic to determine whether to allow or block the traffic. Similarly, an antivirus program might have a blacklist of known malware files that it scans for and removes from a system.

In other contexts, such as email filtering, a blacklist might be used to block spam messages or phishing attacks by listing known spammers or phishers in a blacklist that is checked against incoming emails.

Overall, the purpose of a blacklist is to provide a way to identify and block unwanted or malicious entities, helping to protect systems and networks from potential threats.