Coppers in Bosnia and Herzegovina, Croatia, Macedonia, New Zealand, Peru, the U.K. and the US have been banging on the doors of suspects armed with search warrants. So far 10 people have been arrested. According to the FBI, Facebook's security teams provided assistance to law enforcement and the US Justice Dept. throughout the investigation to help identify the root cause of the botnet, the perpetrators, and which users were affected by the malware.
The Untouchables found millions of machines were infected with Yahos malware, which targeted Facebook users from 2010-2012. This connected them to the Butterfly botnet, which steals credit card, bank details, and other personal identifiable information on infected machines.
The FBI claim that this might be one of the largest botnets and international criminal rings in history, and nicked in more than $850 million.