The SCADA concept stands for a centralized system that controls entire locations, or complicated systems that are spread out over broad areas. Almost all control activities are carried out automatically by remote terminal units or programmable logic controllers. SCADA systems initially relied on modem connections or combinations of direct and radio serial to meet communication needs, though Ip and ethernet can be used at larger sizes such as power plants and railways. Telemetry refers to SCADA systems monitoring or remote management function. Vulnerability by concentration America’s more worrying critical infrastructure issues has to do with the fact that major portions of several critical sectors are concentrated in close geographic proximity; for example Energy, chemical industry and hazardous materials, transportation, and pharmaceuticals. Other examples of vulnerabilities are communications, energy, transportation, government, and evolving threats. The communication sector is huge and diverse covering from traditional voice services, through all internet-related services, to accessing all control devices in every other sector. The next is energy in 2003 the northeast demonstrated the fragility of America’s aging and computer-dependent power grid. The government has a dual role in ensuring the safety and security of the nation’s critical infrastructure as well as in ensuring the safety and security of the government itself another formidable critical building block in the critical infrastructure mosaic. Evolving threats- highlights a single, significant threat that is truly “over the horizon” but is shaping up as a major hurdle to the integrity of all critical infrastructure computer-based sectors.