Simon Cowell -- Security Concerns Over 'X Factor' Girls

Simon Cowell is like an overprotective father when it comes to three girls he's mentoring on "X Factor" -- sources close to the show tell us ... he's deeply concerned for their safety and is taking precautionary measures.

According to our sources, Simon has grown concerned about the safety of the three girls -- Drew Ryniewicz, Melanie Amaro, and Rachel Crow -- after a recent trip to the mall turned into a mob scene.

Our sources says the incident prompted Simon to instruct his personal bodyguards ... they are not to let the girls leave the studio without some form of security. We're told Simon wants the girls to be able to feel safe while doing the kinds of things normal girls do.