On average, since 9/11, the FBI reckons that just over 100,000 terrorism leads each year have come over the transom. Analysts and agents designate them as immediate, priority or routine, but the bureau says every one is covered.

Most people inside the bureau believe that the blown opportunities to head off 9/11 would not recur today. Even among the FBI's doubters, few disagree that the bureau has come a long way.

There is evidence that some of al Qaeda's nuclear efforts over the years met with swindles and false leads.

First developed as a weapon by the U.S. Army, VX is an oily, odorless and tasteless liquid that kills on contact with the skin or when inhaled in aerosol form. Like other nerve agents, it is treatable in the first minutes after exposure but otherwise leads swiftly to fatal convulsions and respiratory failure.

The National Security Agency has broken privacy rules or overstepped its legal authority thousands of times each year since Congress granted the agency broad new powers in 2008, according to an internal audit and other top-secret documents.

Counterterrorism analysts have known for years that al Qaeda prepares for attacks with elaborate 'targeting packages' of photographs and notes.