Issuing authentication tokens is the most reliable method of preventing unauthorized logon, as it provides a strong form of authentication that requires users to present something they have (the token) and something they know (the personal identification number or PIN) to access the system. Authentication tokens are physical devices that generate a one-time password or code that changes periodically and is synchronized with the authentication server. This makes it difficult for attackers to steal or guess the credentials of legitimate users. Reinforcing current security policies, limiting after-hours usage and installing an automatic password generator are not as reliable as issuing authentication tokens, as they do not provide a strong form of authentication and may still be vulnerable to unauthorized logon attempts. References:

[Authentication Token Definition]

 Authentication | ISACA