From this:

A senior al-Qaida operative lived in New Jersey and posed as a student to disguise his surveillance of financial institutions as possible terror targets, officials said Wednesday.

The FBI's top agent in New Jersey, Joseph Billy Jr., confirmed that the operative led an al-Qaida mission to survey the physical layout and assess weaknesses of the Prudential Financial Inc. building in downtown Newark.

While carrying out this reconnaissance operation - which included surveys of the New York Stock Exchange building on Wall Street and Citigroup's headquarters in midtown Manhattan - the man attended several institutions of higher learning in New Jersey, Billy said. He did not identify the schools...

...Discovery of those surveys led U.S. Homeland Security officials to declare an orange alert Aug. 1 for America's financial sector...

...[the reports were detailed...] ...One notation said that using the PATH train system was an option, but pointed out that exact fare should be carried for use at its automated turnstiles to speed a getaway, the official said...

...The documents describe surveillance operations at U.S. financial buildings during 2000 and 2001...

In case that link doesn't work, try the AP reports here or here.

The last link says those sites were surveilled in 2001 and 2002, but the first two say it was in 2000 and 2001. That would seem to be a crucial bit of information. Since the first link is from the reporter who interviewed the FBI agent directly, 2000 and 2001 are probably the accurate dates.

This abuse of our immigration system is, of course, a key way terrorists have entered and stayed in the U.S. See Chapter 3 of the 9/11 Commission Staff Report.