In order to set up a new Group-Based alarm, go to Alarms and select to make an Activity Alarm.
Once on the Activity Alarm, you will select which group(s) you want to make the alarm effective for. In our example below, we don't want our Sales Team and our Support Team to access Facebook. As such, I have selected these groups to apply the alarm. A group such as marketing who may need access to Facebook will not be affected.
This will assist you in determining which users you want to be alerted for without cluttering up the conditions section and making alarms easier to read and set.