The concept of Windows operating system security. The access token contains the security information of the login session. When a user logs in, the system creates an access token, and then all processes running as that user have a copy of the token. Tokens uniquely represent users, user groups and user rights. The system uses tokens to control which security objects users can access and their ability to perform related system operations. There are two kinds of tokens: master token and simulated token. The master token is related to the process; An impersonation token is associated with a thread that impersonates the token. When a process has a token, it means that it has a privilege. Privilege refers to the right of a user process to perform various system operations. For example, shutting down, loading device drivers and changing system time are also privileges. You can grant permissions to users or groups to which users belong.