You can set the following session parameters
Session idle time: the allowable idle time for a user session. Should a user session remain idle for a length of time exceeding that specified as the session idle time, Plesk terminates the current session.
Invalid login interval: an interval between two invalid login attempts within which the invalid login attempts counter is increased. If the time between two invalid login attempts exceeds this value, then the invalid login counter is reset back to 0.
Invalid login attempts: the maximum number of invalid login attempts allowed. Once a user has exceeded this value, he/she is locked out for the time specified as the Invalid login lock time.
Invalid login lock time: the lockout time for a user once the invalid login attempts counter has exceeded its maximum limit. Upon completion of the lockout time, the invalid login attempts counter is reset to zero and the user is again given the ability to login to Plesk.
In order to change the session security parameters:
Select the Session Settings icon on the Server administration page.
Adjust the required settings as desired.