As drone technology has developed and spread, it has posed a number of difficult legal and technical issues, many of which we're still scrambling to address. At this point, flying a drone over the White House is unambiguously illegal, but a problem remains in terms of enforcement. Given the speed and size of many drones, it would be feasible to launch a quick attack before being detected.
They were able to hijack commercial airliners and fly them into buildings almost 14 years ago, so your not really living in the real world if you don't think they have the capability to fly an explosive loaded drone to the white house today. Its only a matter of time before they make an attempt on all their threats.
Just a couple weeks ago in Tijuana, Mexico; a cartel tried to smuggle 3 kilos of meth over the border using a drone, only for said drone to crash in a parking lot unable to carry the weight. Given the improvised nature of terrorist explosives, a civilian drone would be unable to carry enough to cause much damage while still remaining easily portable and capable of flying to the target without crashing.
Any air traffic not cleared would be challenged and shot down almost immediately, if not by the Air Force, then the Secret Service. I think Noble Eagle is still going on, so there are combat air patrols around DC at any given time. There is some nice dakka around DC for intercepting unauthorized air traffic. Sure, some could set up the drone. Deployment is another matter entirely.
Americans like to worry about the imagined capabilities of terrorists, but the reality of the post-9/11 world is this: if they could strike the White House, they would have already. It would be the greatest recruitment ad of all time for them. The fact is they can't. We have better technology, more money, more people and better people. The skies above the White House are the safest in the world.
Security has always been a top priority for the government of the United States and the law enforcers take their jobs very seriously.This is because America has been targeted in the past by terrorists.The white house is always under twenty four hour surveillance to minimise the likelihood of being caught unaware. Considering this, it would be highly unlikely for a terrorist to target the White House and succeed.