The FBI took over the Freedom Hosting servers, which were located in France, and arrested the guy (Eric Eoin Marques) running Freedom Hosting. They then proceed to serve malware to anyone who connected to a site hosted by Freedom Hosting.
How did the FBI find the Freedom Hosting servers in the first place? Were the servers misconfigured leading to an accidental leak? Did they take over entry and exit nodes and conduct traffic analysis? Did the FBI use some Apache 0-day to find it? Or is that the information is not available yet since Eric's trial has yet to begin?