Final answer:
Setting a user's login shell to /bin/false quickly denies them access to the system.
Step-by-step explanation:
To quickly deny a user access to the system set their login shell to /bin/false. This statement is True. When a user's login shell is set to /bin/false, they are unable to log in to the system. Instead, they receive an error message and are immediately logged out. This feature is commonly used in Unix-like operating systems to restrict access for certain users.