  Growing cybersecurity risks in the power grid require that utilities
implement a variety of security mechanism (SM) composed mostly of VPNs,
firewalls, or other custom security components. While they provide some
protection, they might contain software vulnerabilities which can lead to a
cyber-attack. In this paper, the severity of a cyber-attack has been decreased
by employing a diverse set of SM that reduce repetition of a single
vulnerability. This paper focuses on the allocation of diverse SM and tries to
increase the security of the cyber assets located within the electronic
security perimeter(ESP) of a substation. We have used a graph-based coloring
game in a distributed manner to allocate diverse SM for protecting the cyber
assets. The vulnerability assessment for power grid network is also analyzed
using this game theoretic method. An improved, diversified SMs for worst-case
scenario has been demonstrated by reaching the Nash equilibrium of graph
coloring game. As a case study, we analyze the IEEE-14 and IEEE-118 bus system,
observe the different distributed coloring algorithm for allocating diverse SM
and calculating the overall network criticality.
