A power grid strictly depends on information and communication technology. The key role of real-time measurement and information control for the reliable operation of a power grid is the responsibility of the phase measurement units (PMUs). As smart power grids encounter a variety of unauthorized malicious accesses such as cyberattacks, PMU placement is an important problem. In this study, a new algorithm was proposed to specify the minimum number of PMUs in the case of cyberattacks on their communication lines and equipment. In order to analyze complete observability of the distribution system, a range of probable contingencies for the vulnerable lines of a typical power system was discussed. The proposed algorithm implementation shows that the number of required PMUs can be reduced by removing irrelevant information through cyberattack circumstance intervals by using communication equipment potential.