The rapidly increasing dependence on cyber-physical systems (CPS) in building critical infrastructures—in the context of smart cities, power grids, medical devices, and self-driving cars—has opened the gates to increasingly sophisticated and harmful attacks with financial, societal, criminal, or political effects. While a traditional cyber-attack may leak credit-card or other personal sensitive information, a CPS attack can lead to a loss of control in nuclear reactors, gas turbines, the power grid, transportation networks, and other critical infrastructure, placing the nation’s security, economy, and public safety at risk. This talk starts by motivating for the differences between CPS security and cyber-security. To this end, it shows experimental results on non-invasive sensor spoofing attacks targeting the anti-lock brake systems (ABS) in automobiles. As the need for CPS security becomes evident, the talk focuses on a problem known as “secure state estimation.” It aims to estimate the state of a dynamical system when an adversary arbitrarily corrupts a subset of its sensors. The talk concludes by showing, through multiple experimental and simulation results, the effect of different secure state estimation problems on the resilience of CPS against sensor attacks.