Would a NIDS have prevented the Sept. 11 attacks?
The overwhelming majority of the hijackers were in the US legally and had no record with the FBI or other security agency. In other words, they could have obtained a legitimate ID card and the authentication checks prior to boarding the plane would have not have revealed anything that would have aroused the suspicions of authorities. A NIDS offers no security against terrorists who have no record of prior misconduct and are not worried about being identified after the attack (possibly because they will be dead).
