I've yet to be caught.
Also, if I caught my child(ren) with porn, I wouldn't react terribly to it. I'd tell them I did it frequently and I'd use it if the missus wouldn't "lend a helping hand" every now and then. Then I'd probably end up giving them a sex talk. I'd more than likely mention these things if I rememeber them: "Sex is overrated in this society", "A vagina is just an inverted penis with twice the amount of nerve endings, and not a slab of meat to be pelvically tenderized", "That fish-eye lens is used to make the men look bigger *wink wink*, and his size is acceptable, "Fewer women like being "shot" in the face than you think", and "Your first sexual experience with someone will no doubt be terrible". Then I'd probably show them what's in my hard drive, which contains high octane nightmare fuel.
(note: Much of this is for the boy(s) I hope to have one day, and can be switched up for girls)
Then I'd make sure they regularly updated their virus protection and to lock the door, or I'd kick their ass if I saw that action again. That, and not to do it when we have company.
Now I'm hoping to have children one day just for this scenario. I'm not hoping to pay for their therapy.