To view who is currently online and connected to your system you may log in as an administrator and from your Administration Panel click on 'Maintenance' section. Over there, among other options, you will be able to view the Online Users (1) option.
Clicking on Online users will present you a tabular listing of all users that currently online and connected to your system.
Apart from the users' formatted name and the branch they belong to, if any, you will be able to view other information such as when users last accessed the system and when each user was created, as well as, what device your users used to access eFront and what browser.
Finally, from the Operations column (2) you have the option to disconnect any user you want.