Critical infrastructures such as the Supervisory Control and Data Acquisition (SCADA) systems have succumbed to the demands of greater connectivity. Although the scheme of connecting these critical equipment and devices to cyberspace has brought us tremendous convenience, it also enabled certain unimaginable risks and vulnerabilities. These risks and vulnerabilities are very critical to our daily existence and are perilous to ignore. This paper presents an overview of the vulnerabilities of SCADA systems. Also described are proof-of-concept methods of attacking some of these vulnerabilities.