A massive Wells Fargo customer data breach was not the work of a hacker, but of the bank's own lawyer who failed to review the bank's entire set of discovery documents, including information about the bank's wealthy customers, before it was shipped to a litigation adversary.

The event highlights the increasing risks of relying on unfamiliar e-discovery technology—and the potential liability exposure to lawyers.

“Unbeknownst to me, the view I was using to conduct the review has a set limit of documents that it showed at one time,” said Wells Fargo's attorney, Angela Turiano, a New York-based principal at Bressler, Amery & Ross, in an affidavit. “I thought I was reviewing a complete set, when in fact, I only reviewed the first thousand documents.”