Factual error: The White House has security zones inside the building. The terrorists would have had to penetrate many of these, with a security force coming at them from the outside.
Factual error: In the case of an evacuation, the President and VP are separated to different secure areas to avoid precisely the situation that occurs here.
Factual error: When the FBI tactical team arrives, they stay on the perimeter. They had not been told to stand down, and would have assaulted the White House and trapped the terrorists in a pincer movement with the SS attacking from the other side.
Factual error: Near the finale, Kang sends a command to all US based missiles to self-destruct in their silos, thereby detonating their warheads. Ignoring for the moment why "self-destruct in silo" would ever be a desirable scenario programmed into ICBM protocols, detonation of a nuclear warhead requires an extremely precise sequence of events, none of which would include a nearby, conventional explosion. (01:38:20)
Factual error: When one of the terrorists fires an RPG into the security hut, all the windows in the cars standing nearby shatter. Ordinary windshields are made of laminated glass that doesn't shatter, not to mention that at least the SUVs used to transport the prime minister and his escort would surely be armored and therefore possess security glass. (00:28:20)
Factual error: When the AC-130 gunship flies over the White House, some of the Secret Service agents on the roof are firing bolt-action sniper rifles without pulling the bolt back, like a semi-automatic gun. (00:25:20)
Factual error: The Secret Service has more than 3,000 Special Agents across multiple government organizations. Other than those who work the White House and Presidential Detail, it is highly unlikely that others would have any White House access, much less current security codes, as Mike does. Agents would not have passwords to the President's laptop - but Mike is able to log in and delete all the classified data on it.
Factual error: Toward the end of the movie, when the US 7th fleet is ordered to withdraw from the Sea of Japan, two US aircraft carriers are shown maneuvering. One has '67' painted on its island, the other displays '73'. This represents the hull number of the ship. CV-67, the USS John F Kennedy, was decommissioned in 2007, and the F-14 Tomcats on the carriers' decks were retired in 2006.
Factual error: The security booth is a hardened building and would not disintegrate like that from a RPG. It is made to withstand attacks.
Factual error: In the operations room from which the acting president (Morgan Freeman) is directing the crisis there are multiple uniformed military members at the table and seated on chairs behind the acting president. Over Morgan Freeman's left shoulder is seated a man wearing the uniform of an Air Force Senior Enlisted member (can't quite make out of the entire rank, probably a Chief Master Sergeant). The person portraying the Chief is way too old for the rank. On the other hand, a three-star Air Force General is depicted at the conference table and the actor is way too young to have three stars.
Factual error: When Banning is first identified as the agent in the White House, Secret Service Director Lynn Jacob's says he's "ex-Special Forces, Ranger Batallion." Anyone who has ever been in the US Army knows that the Ranger Batallions are not Special Forces units. First, there isn't "a" ranger battalion, there are three, and they are part of the 75th Ranger Regiment, designated by a tan beret (formerly a black beret) which is part of the US Army's Infantry branch, represented by crossed rifles. On the other hand, Special Forces is an entirely different branch unto itself, which is represented by crossed arrows, and Special Forces soldiers wear green berets. (00:48:32)
Answer: Forbes slipped up by mentioning the head bad guy's name. And, as good an agent as Forbes was, it is highly doubtful, not to mention suspicious, that he'd still be roaming around by himself this long after the fall of the White House. Plus Mike ain't stupid and most likely smelled a rat. And he was correct. Forbes was dirty.
Alan Keddie