People who think solitary confinement is necessary give several reasons. Some prisoners are considered dangerous to other people in the prison. Other prisoners might be able to lead crime groups even from inside jail. Also, solitary confinement can be used to stop prisoners from communicating with others because of possible fears about national security. Finally, it may be used for prisoners who are at high risk of being attacked by other inmates, such as pedophiles, celebrities, or witnesses who are in prison themselves. This form of solitary confinement is sometimes called protective custody.