It is obvious that the use of ICS will increase in view of the fact that smart grid systems are rapidly spreading and the concept of smart cities will spread throughout the world in the future projection. Due to business continuity, management control and efficiency, intranet and especially internet network system architecture are now being used in smart network and smart cities instead of isolated network topology. However, this transition has brought emerged with vital vulnerabilities. However, not using security software in ICS in general for the reason that they may hamper business continuity is attracting cyber criminals. On the other hand, the systems being controlled by ICS are performing very vital functions, so the attacks on these systems will have fatal consequences. In this study, the vulnerabilities of ICS, an important component in the management of smart grids, were analyzed. In this context, in the study, denial of service and information disclosure attacks were carried out on two different brands (Siemens and Schneider) real PLCs for examining negative and positive aspects of the PLCs in terms of cyber security weakness.