This is another example of how easy it must be for determined hackers to get into a secure computer system. In this case, Russia is the suspect. CNN tells us about it in How the U.S. thinks Russians hacked the White House.
The FBI, Secret Service and U.S. intelligence agencies are all involved in investigating the breach, which they consider among the most sophisticated attacks ever launched against U.S. government systems. The intrusion was routed through computers around the world, as hackers often do to hide their tracks, but investigators found tell-tale codes and other markers that they believe point to hackers working for the Russian government. ...
To get to the White House, the hackers first broke into the State Department, investigators believe.
The State Department computer system has been bedeviled by signs that despite efforts to lock them out, the Russian hackers have been able to reenter the system. One official says the Russian hackers have "owned" the State Department system for months and it is not clear the hackers have been fully eradicated from the system.
As in many hacks, investigators believe the White House intrusion began with a phishing email that was launched using a State Department email account that the hackers had taken over, according to the U.S. officials.
Director of National Intelligence James Clapper, in a speech at an FBI cyberconference in January, warned government officials and private businesses to teach employees what "spear phishing" looks like.
If the Russians have tapped into the State Department and the White House, why would they have stopped there? If Hillary Clinton was using the insecure private system we've been told about then penetrating it was probably easy.
In that case, the Russians could probably produce all those emails she deleted. Of course, expecting the Russians to cooperate with Republicans is nonsense. If they had anything on Hillary they would most certainly hold onto it for strategic use if she became president. And in the meantime, they'll be doing what they can to see that she does get elected.