Our technology keeps advancing towards a future where everything is connected together. The Internet of Things (IoT) goal is to make every device accessible from the Internet. Even the most common electrical appliances, such as ovens, light bulbs, will have their own IP address, will be reachable remotely. While this enhanced connectivity will definitely improve our quality of life, it also raises serious security, privacy, trustworthiness questions, the resource constrained nature of IoT entities makes traditional security techniques impractical. In this paper, we propose an intrusion detection architecture for the IoT. We discuss the feasibility of employing a commodity device as the core component of the architecture. In particular, we evaluated the performance of the Raspberry Pi, one of the most used commodity single-board computers, while running Snort, a widely known, open source Intrusion Detection System (IDS). Our experiments show that our proposed architecture based on resource constrained devices, such as the Raspberry Pi, can effectively serve as IDS in a distributed system such as IoT.