SharePoint 2013 introduced a new event receiver class called SPSecurityEventReceiver. Custom event receiver class must derive from SPSecurityEventReceiver (Please refer http://msdn.microsoft.com/en-us/library/microsoft.sharepoint.spsecurityeventreceiver.roleassignmentadded.aspx). Using this new event receiver class you will be able to handle the following events
Group Events:
Inheritance Events:
User Events:
Role Events: