For a very good take on all this, check out Tom McGuire at http://justoneminute.typepad.com/main/2005/08/able_danger_mud.html
and Micky Kaus on Slate at http://www.slate.com/id/2124546/?nav=fix

Seems if you do a Nexis search for Atta's name (which McGuire suggests since Able Danger is supposedly using public info database data mining), you get a match saying the FBI arrested him in 1987! Seems Atta's name isn't that uncommon, and there is already a KNOWN terrorist associated with Abu Nidal who the FBI arrested in 1987 and extradicted him to Israel for a bus bombing in 1986.

Since one of Shaffer's reasons why DOD wouldn't pass the info to FBI was concerns over the law, it in fact makes far more sense if the Able Danger mining operation had mismatched the first Atta to the 9/11 Atta, because the original Atta was apparently a naturalized U.S. citizen (and therefore it was in fact illegal for DOD to be targeting him).

In short - Shaffer provides no evidence the Able Danger data mining actually discovered ANYTHING related to the 9/11 hijackers not otherwise known, but may very well (indeed, McGuire argues its likely) have confused two different people in its output that Shaffer is touting today...

Interesting...

Latest update...Yesterday FoxNews was reporting that DOD is preparing to issue a flat out denial that Able Danger EVER identified, by name, any of the 9/11 hijackers. This matches the claim of the 9/11 Commissioners, and is contrary to the Able Danger leaker, Lt Col Tony Shaffer (who has been insisting we had hit on at least the name "Mohammad Atta" prior to 9/11 but never passed it along, and that he'd briefed the 9/11 Commission on this himself...and lets not forget GOP Congressional nutjob Curt Weldon who started all this...).

Well, today on FoxNews (perhaps because he'd now been forewarned?) Shaffer had a change of heart and now says that he briefed the 9/11 Commission in Oct '03 in Afghanistan, and gave a demo of Able Danger but only told them it had helped identify three terrorist cells. No names...

Of course, this constant change of stories (how GOP of him) puts any of his claims into "questionable" status unless verifed elsewhere. Also rarely mentioned, Shaffer was in fact NOT an intell analyst actually working Able Danger. He was in briefing officer, who only told others what he himself had been told...