That's obviously Amanda Seyfriend singing a cover of the classic song "L'il Red Riding Hood" by Sam the Sham and the Pharaohs. She did this for the release of Red Riding Hood earlier this year and it's my favorite thing connected to the movie although it isn't connected to Warner Brothers. I only discovered it a few weeks ago when it was used in an NBC spot for Grimm. (Or a song very similar to it was, I haven't found the spot again and it has been my favorite one.)
The song is available for purchase through iTunes, but not the other usual suspects that I usually prefer since although I use iPods and iPhones, I don't care to be limited to the iTunes format. Still, I have fairy tales playlists--is anyone surprised by this?--and had to have this one for the lists.