Internet of things is a new paradigm that connects the internet to the physical objects of different domain viz. home automation, human health services, and industrial process automation and environmental monitoring. It is deeply presented in our daily activities through various devices. The devices connected with the internet bring many benefits but simultaneously bringing the security issues also. For protecting the network and information systems the intrusion detection system is an important tool. However traditional techniques used for intrusion detection are not sufficient to protect the network consists of specific characteristics like constraint resourced devices and specific protocol stacks. In this paper, we proposed an intrusion detection system for RPL (Routing Protocol for Low power and lossy networks) which is focused on WSN and constrained resources. Proposed IDS follows detection of an attack, IDS placement strategy, and validation process. © 2019 Procedia Computer Science. All rights reserved.