  The Internet of Things (IoT) is increasingly influencing and transforming
various aspects of our daily lives. Contrary to popular belief, it raises
security and privacy issues as it is used to collect data from consumers or
automated systems. Numerous articles are published that discuss issues like
centralised control systems and potential alternatives like integration with
blockchain. Although a few recent surveys focused on the challenges and
solutions facing the IoT ecosystem, most of them did not concentrate on the
threats, difficulties, or blockchain-based solutions. Additionally, none of
them focused on blockchain and IoT integration challenges and attacks. In the
context of the IoT ecosystem, overall security measures are very important to
understand the overall challenges. This article summarises difficulties that
have been outlined in numerous recent articles and articulates various attacks
and security challenges in a variety of approaches, including blockchain-based
solutions and so on. More clearly, this contribution consolidates threats,
access control issues, and remedies in brief. In addition, this research has
listed some attacks on public blockchain protocols with some real-life examples
that can guide researchers in taking preventive measures for IoT use cases.
Finally, a future research direction concludes the research gaps by analysing
contemporary research contributions.
