Security device

A security plug for a fastener having a longitudinally extending female socket adapted to receive a first tool, the plug adapted to be inserted into the female socket to prevent the first tool engaging in the female socket, the plug comprising:

• an outer surface portion complementary to the female socket;
• at least one retaining member for retaining the plug in the female socket, and
• at least one removal portion comprising at least one first engagement surface adapted to be engaged by a second tool having at least one second engagement surface complementary to the at least one first engagement surface, whereby mechanical engagement of the at least one first and second engagement surfaces provides engagement between the second tool and the plug to allow force applied longitudinally by the second tool on the plug to withdraw the plug from the female socket against the action of the at least one retaining member,
• wherein at least one first engagement surface has a self-holding taper has an included taper angle between 1 and 10 degrees.