The massive security breach shows how a global industry of law firms and big banks sells financial secrecy to politicians, fraudsters and drug traffickers as well as billionaires, celebrities and sports stars. [...]
Using complex shell company structures and trust accounts Mossack Fonseca services allow its clients to operate behind an often impenetrable wall of secrecy. Mossack Fonseca's success relies on a global network of accountants and prestigious banks that hire the law firm to manage the finances of their wealthy clients.
Panama Papers and Mossack Fonseca explained, Australian Broadcasting Corporation
What are "shell companies" and how can they be used to hide money or avoid paying taxes?