IP Blacklist
An IP Blacklist is a list of IP addresses that are deemed suspicious, malicious, or untrustworthy, much like a town's list of known troublemakers. Organizations, webmasters, and service providers use IP blacklists to block or limit access from these problematic IP addresses, protecting their networks, systems, and users from potential harm, such as spam, malware, or cyberattacks.
Example
An online store has recently experienced a series of fraudulent transactions from a specific IP address. To protect their business and customers, the store adds the malicious IP address to their IP blacklist. As a result, any future requests from this blacklisted IP address will be denied or flagged for further investigation, reducing the likelihood of future fraudulent activity.