Here are the basics of what the Panama Papers leak is all about. Photo shows the building where the office of Panamanian law firm Mossack Fonseca is located in Panama City, Panama, April 03, 2016. SAN FRANCISCO -- The 11.5 million leaked documents from the Panamanian law firm Mossack Fonseca are providing a treasure trove of data on a hidden world of offshore accounts and murky dealings. "It's becoming much easier than it used to be to store and move very large amounts of data. I would expect this to continue," said John King, a professor of information at the University of Michigan in Ann Arbor, Mich.