The U.S. and her allies are at an ever growing risk of a systemic cyber-assault , with energy infrastructure likely to be hacker 's prime target . The stark warning comes from General Keith Alexander , the retired four-star general and former chief of the National Security Agency . 'The greatest risk is a catastrophic attack on the energy infrastructure . We are not prepared for that , ' he warned . Scroll down for video . Former NSA chief General Keith Alexander has warned that the U.S. and her allies are at an ever growing risk of a systemic cyber-assault , with energy infrastructure likely to be hacker 's prime target . Alexander , who led the U.S. battle against cyber-threats for much of the last decade , was speaking at a private dinner held by IHS CERAWeek in Texas last week , reports the Daily Telegraph . He envisioned a worst case-scenario where hackers targeted oil refineries , power stations , and the electric grid . The payments nexus of the major banks could also be paralysed he warned . 'We need something like an integrated air-defence system for the whole energy sector , ' he said . Alexander listed five countries able to conduct cyber-warfare at the highest level : the US , UK , Israel , Russia and Iran . The current NSA chief Michael Rogers testified late last year that China is capable of cyber-attacks that could cause 'catastrophic failures ' of the water system or the electricity grid . There is no suggestion that China has an intention to use its power to damage US infrastructure . NSA officials are less confident that Iran will show self-restraint . Alexander also voice his concern about the hacking threat from a terrorist organization such as ISIS . He said that the U.S. and her allies had failed to check the advance of ISIS and its expanding network of franchises across the Middle East .
General Keith Alexander has warned that the Texas and her allies are at an ever growing risk of a systemic cyber-assault . He predicts that energy infrastructure would be hacker 's prime target . 'We are not prepared for that , ' he warned in U.S. last week . Also voiced his concerns about the hacking threat from a terrorist organization such as ISIS .