At least some content in this article is derived from information featured in Fantastic Beasts and Where to Find Them (film). As such, spoilers will be present within the article.
Director of Magical Security is the chief security officer for the protection of the magical community in the United States of America. It is a high-ranking position within the Magical Congress of the United States of America, likely a rough equivalent of the No-Maj post of Secretary of Homeland Security.
The Director of Magical Security was responsible for ensuring the safety of American witches and wizards. They would supervise the efforts to conceal magic from the No-Majs, supervise the Federal Bureau of Covert Vigilance and No-Maj Obliviation and the Federal Wand Permit Office. MACUSA could use wand permits to disclose the identity of criminals, which would also play a part in keeping the wizarding society in America safe from such individuals.
In 1926, Percival Graves, a former Auror, served as Director of Magical Security. He also held the position of Head of the Department of Magical Law Enforcement under President Seraphina Picquery, in which capacity he was described as the President's "right-hand man". Percival presumably had even many more duties on his plate than safeguarding the community in this manner, though it seemed to be considered his most important duty.
By December 1926, Percival Graves was being impersonated by Gellert Grindelwald who acted in the capacity of Director to try and protect the wizarding community from the damage caused by the creatures that escaped Newton Scamander's suitcase. He also used the position to try and find an Obscurial. He acted as Percival to befriend Credence Barebone who he believed could lead him to the Obscurial until he discovered that it was in fact Credence.
Notes and references
|Magical Congress of the United States of America|