Security screws are similar in design to conventional screws. However, there is one main difference: security screws come in many different shapes and sizes and tend to have a unique drive style, for which you require specific tools. The unique drive style is because a security screw's primary purpose is to deter tampering and avoid removal by unauthorized personnel. Excellent examples are assemblies or systems in public areas, exposing them to vandalism or sabotage. 

If you imagine a simple slotted head screw, it is very easy for someone in public to undo that screw with a simple flat-headed screwdriver or even with a small coin in their pocket. The security screw's purpose is to prevent this and deter vandals from attempting to undo the screw.

Security screws are tamper-proof and are mostly used in securing important equipment like ATM machines, jail grills, license plates, cars and other critical equipment. Security screws are tamper-resistant because they cannot be taken apart by normal drivers. This is because the head of the security screws are unique from one batch to another and a special driver is provided to users and cannot be duplicated elsewhere.