Between 2010 and 2014 the US Department of Energy was hit by hackers over 150 times. Just pause and think about that for a moment. In the span of four years, the federal organization that helps regulate our power grid, energy labs and nuclear weapons was successfully infiltrated 159 times. Almost as terrifying, the department was constantly under attack according to records obtained by USA Today. During that time there were 1,131 attempts made to break into the DOE's systems.
The government hasn't said what if any data was stolen, though the extremely sensitive nature of what the Department of Energy oversees is certainly cause for concern. If information about our nation's energy grid were to windup in the hands of a terrorist organization or a country like North Korea, it could prove extremely problematic... to put it lightly. The security of the power grid and our nuclear stockpile has been the topic of repeated handwringing from experts. And, even with the administration's renewed focus on cybersecurity, bad actors have proven time and time again that they can break into government systems with enough time and effort.
In the last year alone attacks on the Office of Personnel Management saw over 21.5 million Social Security Numbers stolen, and tax records of over 300,000 people were compromised in a breach of the IRS. Add the near-constant barrage of attacks on the Pentagon (which occasionally lead to its networks going down) and breaches of White House email servers and it becomes clear why the Obama administration has moved to make cybersecurity a priority during his second term.
A good place to start is probably with updating passwords. A security audit in October of 2014 found 41 servers and 14 workstations at the DOE "were configured with default or easily guessed passwords."