For the past couple of months, hackers have breached the computer networks of companies that operate nuclear power facilities in the US, according to a new report from federal law enforcement officials. From a report: One of the companies targeted was the Wolf Creek Nuclear Operating Corporation, which operates a nuclear facility near Burlington, Kansas, according to a joint report issued last week by the FBI and Department of Homeland Security and described by The New York Times. The report carried an urgent amber warning, the second-highest rating for the severity of the threat, the Times reported. Organizations running the nation's energy, nuclear and other critical infrastructure have become frequent targets for cyberattacks in recent years. In a 2013 executive order, President Barack Obama called cyberattacks "one of the most serious national security challenges we must confront."