Identify this screw head (was: Security Torx)
This is a tamper proof torx screw. There are torx bits with a hole in the center that will remove them, if you are bold you can try smacking the center pin with a punch at an angle (small ones usually snap off) and then a standard torx bit can be used to remove it.  Check  online and I bet you can find a tamper proof bit kit for under 15$.