With the increase of Internet of Things (IoT) applications, the number of devices communicating over the Internet is also increasing. These devices are generating numerous amounts of sensitive data that are being communicated over an unprotected network. The manufacturers are providing the least preferences for the device-level security due to resource-constrained properties of the IoT devices. The existing research has shown large computational cryptographic solutions that both consume power and occupy more space on the device. Thereby, it is required to develop lightweight cryptographic solutions that are suitable for low-powered resources of IoT applications. In this chapter, a detailed study of various attacks that can be encountered on various layers of IoT architecture is generalized with possible lightweight measures. Also, threat modeling using Microsoft’s threat modeling tool is explained that helps in the early identification of threats in IoT applications. Finally, security practices that should be followed by enterprise IoT are covered.