The purpose of this paper is to chalk out the criticality of the most important pillar of the Internet of Things (IoT), i.e., Security and Privacy (S&P). IoT has seen its journey from implausible and impossible to sustainable and tenable. Its rate of expansion into various grounds from agriculture to sports; personal health to intelligent traffic detection; waste management to smart homes is astonishing, dramatic, and unforeseen. With such vast adaptability and functionality, its security remains the biggest concern because, in contrast to the traditional networks, IoT faces huge vulnerabilities, some of which are inherent and others explicit. The existing security solutions cannot be implemented in IoT because of its unique characteristics. Therefore, there is a dire need to develop novel security procedures befitting IoT. This paper spots the features that are peculiar to IoT and concurrently analyzes the security threats, and challenges they pose. This work also provides a glimpse of the major IoT implementations with their particular security requirements and challenges. Moreover, this paper critically evaluates the proposed countermeasures to security attacks on different features and why they cannot be used in IoT environments. Also, it is found that most of the security solutions used in IoT devices are inspired by Wireless Sensor Networks (WSN, but the striking differences among the two make them inadequate in IoT. The security requirements and challenges peculiar to various IoT services are also identified. To assist the researchers in remaining up-to-date, we for the first time have thoroughly expressed some of the most famous and practical attacks faced across the world in the recent past, how much damage they caused, how many financial losses were faced, etc.