The failure of an industrial network can have severe repercussions,
as detailed in Section II-A3. Such failure could be
accidental, or caused by malicious intent. Prevention of these
failures is provided by reliability and security respectively,
although the two aspects of the systems are tightly interlinked
- security flaws can be viewed as reliability flaws that are
exploited deliberately [42]. However, where the network itself
cannot, or has not, addressed these flaws through its own
reliability considerations, additional measures must be put in
place to prevent access to the flaws and increase the security
of the system. Securing industrial networks has become a
prerequisite for securing critical infrastructure at a national
level. This is true for all industrialised nations and a greater
dependence on the development and implementation of industrial
network security is realised as greater levels of automation
and computer-dependence is implemented within chemical
processing, utility distribution and discrete manufacturing [43],
[44].