With the ever-growing rise in smart devices and their applications in most sectors, there is a need for security as the information is transmitted using a wireless medium of transmission. One of the most profound health care devices is the implantable medical devices used for monitoring and control of vital organs such as neural systems, heart, and cochlear implants. Although IMDs provide quick and cost-effective diagnostic features to the patients there exist some design constraints and software threats that need attention. There is a chance of leakage of confidential data pertaining to the person with IMD by attackers, thereby manipulating the parameters of the devices causing the patient’s life to be at high risk. In our paper, the different types of IMDs and their constraints are addressed. As the emphasis is on the security aspects of these devices, their requirements, the attack vectors, the type of attacks encountered, and the protection mechanisms implemented to date are also discussed.