Blacklisting is the practice of creating a list of individuals, organizations, or entities that are deemed undesirable or untrustworthy. This list is often used to deny access to services, employment, or opportunities. For example, companies may blacklist former employees who were found to be dishonest or unreliable, preventing them from being hired elsewhere. In the digital world, blacklisting can also refer to blocking certain websites or email addresses to protect users from spam or harmful content. Cybersecurity measures often involve blacklisting known threats, such as malicious software or phishing sites, to enhance online safety and security.