Security in embedded systems is an area of major concern to system designers. Embedded devices are becoming potent, autonomous, and highly connected. They are an integral part of digital computing and communication. However, the more powerful, autonomous and connected these systems get, the more vulnerable they are to security attacks. Attacks on these systems are getting more and more sophisticated. Hence, it is essential that these devices have good protection against attacks. Security in embedded systems differs from the security in other electronic systems like desktops and servers. Embedded systems have to operate under strict constraints to perform its functionalities. In addition to performing the system’s functionalities, these systems have to support cryptographic algorithms, security protocols and several other security measures. Finding a design to enforce security in systems using the various security mechanisms within the constraints posed by embedded system is a severe challenge. In this paper, we outline the various known attacks that embedded systems face and the techniques that employed to simultaneously prevent and counter the attacks while performing the system’s functionalities efficiently under several constraints.