What screwdriver do I need for this 'star' shaped fitting?
You need a Torx bit also sometimes referred to as star drive.

You may be able to get a fixed screwdriver with the right size one but it's generally a better deal to just get a bit assortment and mount an adequately sized one on some sort of a socketed shaft, depending on the application.



Note: Torx drive invented originally by Camcar Textron to eliminate the rounding issue standard hex drive bits suffer.