What does Sid mean?

Sid is a unique identification number, that is, a security identifier, which is a unique number to identify users, groups and computer accounts.

1.SID is a unique identification number.

The computer uses the SID to track each account: If the administrator account is renamed, the computer still knows which account is the administrator account. This is because SID is different from name, and it will never change.

For example, you can rename the administrator account on your computer and still use it as an administrator, because what Windows really cares about is not the name; Windows still knows that the account is an administrator account, because the SID remains the same no matter how the account name changes.

Secondly, SID, also known as security identifier, is a unique number that identifies users, groups and computer accounts.

When an account is first created, a unique SID will be issued to each account on the network. Internal processes in Windows 2000 will refer to the account's SID, not the user name or group name of the account. If you create an account, delete it, and then create another account with the same user name, the new account will not have the power or authority to authorize the previous account because it has a different SID number. A security identifier is also called a security id or SID.

SID's role

After the user is authenticated, the login process will give the user an access token, which is equivalent to the user's ticket to access system resources. When a user tries to access system resources, an access token will be provided to Windows NT, and then Windows NT will check the access control list of the object that the user tries to access.

If the user is allowed to access the object, Windows NT will assign the appropriate access rights to the user. The access token is provided by the login process when the user is authenticated, so changing the user's permissions requires logging out and logging in again to get the access token again.

If two users have the same SID, the two accounts will be recognized as the same account. In principle, if the number of accounts increases indefinitely, the same SID will be generated. Generally speaking, SID is unique, which is determined by the sum of computer name, current time and CPU time spent by current user mode thread to ensure its uniqueness.