Which of the following is a common practice for maintaining club security?

Maintaining club security is crucial for organized crime groups, and one of the most effective practices is keeping out informants. Informants can jeopardize the operations and safety of the organization by providing law enforcement and other external entities with crucial information about the club's activities, vulnerabilities, and personnel. By actively working to identify and exclude individuals who may act as informants, clubs can protect their interests and maintain their operational security.

Other practices mentioned, such as an open door policy for new riders, regularly updating the club emblem, and advertising club events publicly, do not contribute to maintaining security effectively. An open-door policy might lead to the inclusion of individuals who could potentially expose the club to risks. Regularly updating the club emblem is more about branding or internal culture than security, and advertising events publicly can attract unwanted attention from law enforcement and rival organizations, further compromising the club's safety.