By the time the conference call ended, it was nearly midnight at Bank of America’s headquarters in Charlotte, N.C., but the bank’s counterespionage work was only just beginning.

A day earlier, on Nov. 29, the director of WikiLeaks, Julian Assange, said in an interview that he intended to “take down” a major American bank and reveal an “ecosystem of corruption” with a cache of data from an executive’s hard drive. With Bank of America’s share price falling on the widely held suspicion that the hard drive was theirs, the executives on the call concluded it was time to take action.

Since then, a team of 15 to 20 top Bank of America officials, led by the chief risk officer, Bruce R. Thompson, has been overseeing a broad internal investigation  scouring thousands of documents in the event that they become public, reviewing every case where a computer has gone missing and hunting for any sign that its systems might have been compromised.

In addition to the internal team drawn from departments like finance, technology, legal and communications, the bank has brought in Booz Allen Hamilton, the consulting firm, to help manage the review. It has also sought advice from several top law firms about legal problems that could arise from a disclosure, including the bank’s potential liability if private information was disclosed about clients.