The Internet of Things (IoT) is the new revolution of internet after PCs and servers-clients communication now sensors, smart object, wearable devices and Smartphones are able to communicate. Everything surrounding them can talk to each other. Life will be easier and smarter with smart environment, smart homes, smart cities and intelligent transport and healthcare. Billions of devices will be communicating wirelessly is a real huge challenge to their security and privacy. IoT requires efficient and effective security solutions which satisfies IoT requirements, the low power, small memory and limited computational capabilities. This paper addresses various standards, protocols and technologies of IoT and different security attacks which may compromise IoT security and privacy.