It looks like a cyberattack that hit the White House last year by Russian hackers was a bit more serious than originally presented. The biggest takeaway is the fact that president Obama's personal emails were accessed, including both sent and received messages. That's the downside; the upside is that it appears absolutely no classified information had been accessed.
This security breach does raise some major concerns, though, ones that the White House have taken extremely seriously. At the time of the attack, officials met on a nearly daily basis to keep apprised of the situation. One official said a major reason for its seriousness is that it the attack involved Russia.
It doesn't appear that Obama's BlackBerry was accessed by the Russians, which is the only thing that helps officials keep calm; some of his most important, sensitive messages are sent and received on this device.
The New York Times notes that at the White House, most officials have two computers. One is connected to the open Web, while the other is restricted to a very secure, highly monitored network. That might seem like a bulletproof implementation, but of course there's humans using these computers - sometimes, less-than-ideal messages are going to be sent or received through the computer connected to the open Web.
This attack overall could have been a lot worse, but given the information that was retrieved, it looks like the White House has some extra security measures to put into place.