Water is a fundamental resource for human and economic welfare and modern society depends on complex, interconnected water infrastructure to provide reliable safe water supplies. This infrastructure is vital for human welfare and economic development and it is vulnerable to intentional disruption from war, intrastate violence and, of more recent concern, terrorism. There is a long history of using water as a political or military target or tool. Water resources and systems are attractive targets because there is no substitute for water. Whether its lack is due to natural scarcity, a physical supply interruption or contamination. The cheapest and lowest-cost way to deal with natural and unnatural calamities, Acts of "passive defense" And security precautions to prevent the occurrence of extensive damage to sensitive and critical centerecause prevention is always better than cure. This paper reviews the history of past attacks on water systems and the most pressing vulnerabilities and risks facing modern water systems. Suggestions for ways to reduce those risks are also presented. As well as using comments authorities, experts and the executive agencies, university professors and by using a questionnaire method and Carver matrix technique (as an acceptable method to different applications) The potential vulnerability of drinking water systems have been identified and evaluated. The results showed that surface waters with scores of 61, diversion dam with scores of 58 and the main water distribution lines with scores of 41 Respectively, are infecting vulnerable to damage points, explosions and sabotage in operation. also The results showed that several factors such as infrastructure and unprotected tanks, inefficient remove systems for some of the contaminants in water, Large and old treatment plants, open and scattered distribution systems, low real-time monitoring capabilities, Lack of information protection and SCADA systems and the high cost and slow pace of repairs, has made it difficult to protection of this infrastructure and this has increased the vulnerability of these systems against various threats. At the end,Protection and treatment strategies and suggestions. Based on the principles of passive defense to improve areas of weakness are provided. Keywords: Water infrastructure,Vulnerability,Passive Defense,drinking water,Carver matrix