From NBC News:
U.S. intelligence has assigned more than 1,000 spies to Olympic security as part of a highly classified effort to protect the Rio 2016 Summer Games and American athletes and staff, NBC News has learned.
Hundreds of analysts, law enforcement and special operations personnel are already on the ground in Rio de Janeiro, according to an exclusive NBC News review of a highly classified report on U.S. intelligence efforts.
In addition, more than a dozen highly trained Navy and Marine Corps commandos from the U.S. Special Operations Command are in Brazil, working with the Brazilian Federal Police and the Brazilian Navy, according to senior military officials.
The U.S. military, as expected, has placed larger military units on call should a rescue or counterterrorism operation be needed, the officials said.