Security Device

A security plug for a fastener having a 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:

• a first outer surface portion complementary to the female socket;
• a first longitudinally extending recess having a frusto-conical first engagement surface;
• first protrusion extending longitudinally within said first recess;
• a magnetic retaining member for retaining the plug in the female socket, wherein
• the first engagement surface is adapted to be engaged by a second tool having a second surface complementary to the first engagement surface, whereby engagement of the 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 retaining member.