Hackers love "top" torrents. They will upload a 64-episode pack that is actually a virus wrapped in an MKV shell. Or, they will hide malware in the .exe file of a "fansub installer." Stick to known release groups on reputable indexers—but even then, no public tracker is 100% safe.
A legitimate top-tier torrent for FMA:B will have: i fullmetal alchemist brotherhood download torrent top
Search results for downloads or torrents of Fullmetal Alchemist: Brotherhood Hackers love "top" torrents