In exchange 2013 you can setup users with various permissions. Sometimes users need to be members of groups for certain reason that also give them access to the Exchange 2013 ECP. With a power shell command we can stop users accessomg the Exchange 2013 ECP.
To do this drop to power shell and run the following command.
Set-CasMailbox -Identity "Allen" -ECPEnabled $False
Here we use the Set-CasMailbox command, we specify the Allen account we say the ECPEnabled property is false.
When the user tries to log into the ECP they will see see the login screen however when they enter their credentials they will see an Access Denied message. The user is now banned from the Exchange 2013 ECP, this also applies to Exchange 2010 and Exchange 2007. See the diagram below.