  Internet of Things (IoT) aims at providing connectivity between every
computing entity. However, this facilitation is also leading to more cyber
threats which may exploit the presence of a vulnerability of a period of time.
One such vulnerability is the zero-day threat that may lead to zero-day attacks
which are detrimental to an enterprise as well as the network security. In this
article, a study is presented on the zero-day threats for IoT networks and a
context graph-based framework is presented to provide a strategy for mitigating
these attacks. The proposed approach uses a distributed diagnosis system for
classifying the context at the central service provider as well as at the local
user site. Once a potential zero-day attack is identified, a critical data
sharing protocol is used to transmit alert messages and reestablish the trust
between the network entities and the IoT devices. The results show that the
distributed approach is capable of mitigating the zero-day threats efficiently
with 33% and 21% improvements in terms of cost of operation and communication
overheads, respectively, in comparison with the centralized diagnosis system.
