From Tech Insider:
An obscure law firm in Central America is the source of what's being called the largest information leak in history.
Emails and documents reveal how the world's richest and most powerful, from Vladimir Putin to the prime minister of Iceland, hide their business dealings using offshore tax havens and shell companies.
For the past year, hundreds of journalists from around the world secretly analyzed terabytes of data uncovered from Mossack Fonseca, a Panama-based law firm with offices around the world. Their findings were collectively published on April 3 as the Panama Papers.
About a year ago, an anonymous source contacted German newspaper Süddeutsche Zeitung with data from Mossack Fonseca, a relatively unknown law firm based in Panama that specializes in creating shell companies. These shell companies are held in countries with strict privacy laws and used to obfuscate business dealings.