SCADA systems monitor and control important national infrastructures such as power generation, distribution, water supply, transportation and manufacturing. However, due to the convenience and popularity of the Internet, these systems can control these infrastructures remotely, which may cause the global network security threats. Therefore, these control systems require strong security protection, because the failure of SCADA systems can cause serious economic depression and fatal national security. This paper tries to study and provide the related security tools and technologies to protect the SCADA systems.