They are probably either Torx headed screws or security screws.
Do a Google search for Torx head and you will see the classic star shaped recess.
If there is a central pin as well, that is a security version. There are a range of other securty heads for screws; some with a 3 point posidrive, some that can be undone with flat blade that has a central cutout. The variations are legion.
Here is a typical set of security drive bits. You can also try Amazon, EBay, etc. for cheaper alternatives:
http://www.screwfix.com/p/titan-security-screwdriver-bit-set-32-pieces/1445h
XXX, July 2016
