  Security is one of the most relevant concerns in cloud computing. With the
evolution of cyber-security threats, developing innovative techniques to thwart
attacks is of utmost importance. One recent method to improve cloud computing
security is Moving Target Defense (MTD). MTD makes use of dynamic
reconfiguration in virtualized environments to "confuse" attackers or to
nullify their knowledge about the system state. However, there is still no
consolidated mechanism to evaluate the trade-offs between availability and
security when using MTD on cloud computing. The evaluation through measurements
is complex as one needs to deal with unexpected events as failures and attacks.
To overcome this challenge, we intend to propose a set of models to evaluate
the availability and security of MTD in cloud computing environments. The
expected results include the quantification of availability and security levels
under different conditions (e.g., different software aging rates, varying
workloads, different attack intensities).
