WASHINGTON ( CNN ) -- Computer hackers have embedded software in the United States ' electricity grid and other infrastructure that could potentially disrupt service or damage equipment , two former federal officials told CNN . The ex-officials say code also has been found in computer systems of oil and gas distributors . The code in the power grid was discovered in 2006 or 2007 , according to one of the officials , who called it `` the 21st century version of Cold War spying . '' Department of Homeland Security Director Janet Napolitano would not confirm such a breach , but said Wednesday that there has been no known damage caused by one . `` There have been , to my knowledge , no disruptions of power on any grid caused by a deliberate cyberattack on our infrastructure -- on the grid , '' Napolitano said . `` Nonetheless , we remain in constant protection , prevention , education , resiliency mode and we work with the utility sector particularly on that . '' Watch security officials explain threat » . The U.S. power grid is n't the only system at risk . The former officials said malicious code has been found in the computer systems of oil and gas distributors , telecommunications companies and financial services industries . Napolitano said the vulnerability of the nation 's power grid to cyberattacks `` has been something that the Department of Homeland Security and the energy sector have known about for years , '' and that the department has programs in place to fight such attacks . Security experts say such computer hacking could be the work of a foreign government -- possibly Russia or China -- seeking to compromise U.S. security in the event of a future military conflict . Former CIA operative Robert Baer said he is not aware of a specific breach like the one the former officials describe . But he said people in the intelligence community assume that such attacks from countries like China go on all the time . `` Their foreign intelligence service has been probing our computers , our defense computers , our defense contractors , our power grids , our telephone system . ... I just came from a speech at the national defense university and they were hit by the Chinese trying to get into their systems , '' Baer said . `` They are testing and have gotten in portals . It 's a serious threat . '' Baer said if the software was embedded by a foreign government , he doubts it would be used to launch a surprise attack . Instead , he said , that government likely would keep the bugs in place in case of a future conflict with the United States . `` It 's deterrence in the event of war , '' he said . `` They will have another weapon at their disposal , which will be to turn off our power . '' When the coding is found , it can be destroyed . But experts said that 's easier said than done . `` If you have somebody who knows what they 're doing writing that code and embedding it in a clever way , you can look right at it and not recognize it , '' said Scott Borg , director and chief economist at the U.S. Cyber Consequences Unit , an independent research institute . And even when it 's found , Borg said , confirming the source of a cyberattack can be next to impossible . `` Anonymity is a fact of life in the cyberworld , '' he said . `` It 's very easy to run an attack through somebody else 's computer . It 's very easy to embed code in Russian or Chinese when you 're not Russian or Chinese . `` So it 's very difficult to be confident on where anything like this comes from . '' Critics of the utilities industry have accused it of not doing enough in the past to defend against cyberassaults . But Ed Legge , spokesman for the Edison Electric Institute , which represents shareholder-owned electric companies , said the industry takes the threat seriously and has made progress in closing some of the loopholes that would allow such attacks . President Obama has started a 60-day review of all the nation 's efforts at cybersecurity that is expected to be completed by April 17 , Napolitano said . While utility grids are owned by industries , not the government , Napolitano said her department will continue working with power companies and other industries to help prevent an attack that could cripple power or other vital services . `` Can we continue to work to enhance efforts within critical infrastructure like the utility grid ? Yes , '' she said . `` Are we continuously looking for ways to enhance and educate for the prevention and protection of the cyberworld ? Absolutely . `` Is this a priority of the president 's and of all of us that are involved with safety and security ? You bet . ''
2 ex - federal officials say U.S. electrical grid , other countries targeted . Homeland Security does n't report a code , says no deaths caused by one . FBI says this kind of code can be difficult to detect .