There are many misconceptions about this. Lotsa yuks at inmate expense. The misconception being that whoever winds up in jail deserves whatever they get, even if that means gang rape resulting in anal lacerations requiring surgery. If an inmate is new to the prison, not affiliated with prison gangs ,unpopular with guards or financially unable to pay for protection, they are easily targeted by gang rapists.
Guards have many times been the instigators in such attacks, setting up the inmate for rape.
Well think again. Guards know what every inmate is doing at any time and place. Apparently they only have eyes for masturbation, not gang rape. Unfortunately, prison rape is more than 'mans inhumanity to man' where prison brings out the worst in a person. This inhumanity is being encouraged by correctional officers who in turn are encouraged by their superiors.