It's true, the Brazilian government has released photos of an "uncontacted" tribe near the Peru border. They say they're showing these pictures to prove the existance of the tribe and to protect them from the illegal logging industry, which is apparantly pretty huge. They say there are probably about 100 tribes like this left in the world. Link to video.
This reminds me of a similar tribe I read about in an old high school textbook, the Tasaday. I thought this was so fascinating that I Googled it, only to find out that the entire thing was an elaborate hoax! Crazy!!