  Penetration testing increases the security of systems through tasking testers
to 'think like the adversary' and attempt to find the ways that an attacker
would break into the system. For many systems, this can be conducted in a safe
and controlled way; however, some systems are so critical to human life and
safety that the risk of their failure or disablement due to active penetration
testing cannot be assumed. These systems are also critical to evaluate the
security of, to prevent attackers from disabling them or causing their
maloperation; however, this must be done in a manner that doesn't risk the very
malady that testing seeks to avoid through the testing process itself. This
paper presents P2SCP, a paradigm for penetration testing of systems that cannot
be subjected to the risk of penetration testing. It discusses how data
collection, the creation of digital twins and cousins and evaluative analysis
can be utilized to conduct virtual penetration tests on critical infrastructure
systems. This proposed paradigm is analyzed through the use of several case
studies.
