An overview is given of attacks on hardware security by introducing the four attack classes: logical attacks, physical observative attacks, physical fault injection attacks, and physical manipulative attacks. Descriptions and examples are given for each class of attack. Additionally, typical countermeasures for products to prevent successful attacks are listed and explained. Thereby, an introduction to hardware security is given as well as information shared for advanced readers. A methodology is suggested for a rating scheme on the countermeasures to allow easier product selection for given use cases and applications. Finally, the definitions of related rating tables are identified.