You can break the little pin in the center of the head with a small nail or screwdriver if you don't have the tamper proof torx tool, normal torx will then fit.
tamper screw sets http://www.ebay.co.uk/itm/100-PIECE...t=UK_Hand_Tools_Equipment&hash=item5af720518a
They don't all use torx tamper proof screws...
lSome servo/abs units use a different type of security screw. It's looks like the Isle of man emblem with three leg type of indentations on the screw head.. If you have these just hit a torx bit into them, they're quite soft.