If you have created a secondary user with in your Plesk subscription (eg, for your web developer), leaving it enabled when it's not required can be a potential security risk. Rather than deleting it and re-adding when it's required, you can simply disable the account until it's requried again. This will prevent the user from being able to login to Plesk or via FTP.
- Login to Plesk.
- Select the subscription the user is connected to.
Click on the users tab:
- Click on the name of the user you wish to disable.
Click on "Change settings":
Untick "User is active" and then click "OK"
- You have now successfully disabled the user.