This security setting determines whether pressing CTRL+ALT+DEL is required before a user can log on.
If this policy is enabled on a computer, a user is not required to press CTRL+ALT+DEL to log on. Not having to press CTRL+ALT+DEL leaves users susceptible to attacks that attempt to intercept the users' passwords. Requiring CTRL+ALT+DEL before users log on ensures that users are communicating by means of a trusted path when entering their passwords.
If this policy is disabled, any user is required to press CTRL+ALT+DEL before logging on to Windows (unless they are using a smart card for Windows logon).