Wall Street was atwitter late on Monday when WikiLeaks’ founder, Julian Assange, disclosed in a Forbes interview that the organization’s next target was a major American bank, with a major data reveal to come early next year.

Of course, he didn’t specify which bank; Mr. Assange is, among other things, skilled at building up suspense for his organization’s data dumps. But in this case, he may have let the cat out of the bag a year ago.

In an October 2009 interview with Computerworld, Mr. Assange said that he had obtained copious amounts of data from a Bank of America executive’s hard drive.

Fabrice Coffrini/Agence France-Presse — Getty Images

From the Computerworld piece:

“At the moment, for example, we are sitting on 5GB from Bank of America, one of the executive’s hard drives,” he said. “Now how do we present that? It’s a difficult problem. We could just dump it all into one giant Zip file, but we know for a fact that has limited impact. To have impact, it needs to be easy for people to dive in and search it and get something out of it.”

Scott Silvestri, a Bank of America spokesman, said in a statement: “More than a year ago WikiLeaks claimed to have the computer hard drive of a Bank of America executive. Aside from the claims themselves we have no evidence that supports this assertion. We are unaware of any new claims by WikiLeaks that pertain specifically to Bank of America.”

At five gigabytes of data, WikiLeaks’ treasure trove could amount to more than 600,000 pages of information — far larger than all the recent books about Merrill Lynch’s downfall put together.

WikiLeaks has already demonstrated the power of its organized data exposés — having the secretary of state publicly attack you for unveiling a quarter-million confidential diplomatic cables isn’t terribly common, as far as we know — so it remains to be seen what the organization has in store for the bank it is targeting.

All Mr. Assange told Forbes is that the information would expose what he called an “ecosystem of corruption.”

What could be in the data he’s uncovered? Whether the firm is Bank of America or not, as long as it’s a major United States institution, chances are that it will involve the foreclosure fracas of earlier this year. Or it could involve the “putback” controversy over mortgage-backed securities. Or it could involve dealings with the federal government regarding the financial bailout.

There may be more damage to come: In a followup to his original piece, Forbes’s Andy Greenberg writes that WikiLeaks has unpublished documents from multiple financial firms.

Ever modest, when asked about the impact the impending “megaleak” may pose, Mr. Assange told Forbes, ” It could take down a bank or two.”

(Via The Huffington Post and Business Insider.)