Once the alarms have been sent to CSPM from the sensor you can not filter them from the Alarm Viewer, but you could sort them by the Source and Destination Location:
Move the Source Location to the first column, and move the Destination Location to the second column. At this point the alarms should be sorted in the following order "IN,IN", "IN,OUT", "OUT,IN", and finally "OUT,OUT". At this point you can delete all of the "OUT,OUT" alarms if you like.
For future alarms you can setup a filter to prevent any "OUT,OUT" alarms from being generated by the sensor.
Refer to the CSPM Users Guide for instructions: http://www.cisco.com/univercd/cc/td/doc/product/ismg/policy/ver22/config/svsigs.htm#xtocid1368614
Select all of the signatures, and select OUT for the Source and Destination.
