The Washington Post and The New York Times both run stories on the origin of the "intelligence bonanza" which partly explains the raising of nthe threat level in New York, New Jersey and D.C. The two stories vary a bit in detail, but it does seem to be the case that the arrest of a 25 year old computer geek (al Qaeda IT guy?) a few weeks ago has
led to a "treasure trove" of information, including getting a "virtual playbook of the tradecraft al Qaeda surveillance teams use."
Interestingly (and probably correctly) the arrest of this fellow was not made public at the time of his arrest (July 13).