For those using Unifi with stock DIR-615 router, it is very easy to block off PPS using the router. Just go to "Advanced" - "Filter Rules". Then get the MAC address of the client whom u wanna block. Block port from 1900 to 64430. Save Setting and Reboot router. They can now surf normally, but PPS will be blocked!

Here's a screenshot:
[attachmentid=2845658]

The best thing is during low-peak hour when you allow PPS you can always uncheck the tick box, and re-check whenever you need the bandwidth again, and act like nothing happened ...... 

Worked for me ......