My attitude does not stem from prudishness; I think teenage boys are surrounded by enough beautiful girls every day that they should be able to get by on their imaginations until they're at least 20.
By getting into erotic material too early, I wonder if they aren't stifling their own mental erotic capabilities.
My sense is that he's certainly going to masturbate as much as he wants (and neither my wife or I want to make him feel guilty about it) but that he will, somehow, seek out the materials he wants - so it's better to guide him rather than refuse complete access to porn. You're obviously a parent who cares a lot, although your question is a shocking one.
I think you're right to cut him off from Internet porn.
This is my little girl and I do not know what to say or do about this situation.
I have always tried to be very open with my kids about sex, drugs, alcohol, etc., and I am glad she feels comfortable to confide in me, but I just never imagined it would be something like masturbation and at such a young age.
We definitely know that a lack of sex education leads to early sexual experimentation, so I suggest you explain to your daughter what masturbation is in the larger context of sexual behavior, and soon.
However, as the type of pictures available on-line can be quite extreme, I'm going to cut him off from that source of visual material.
I don't think her behavior is anything to worry about or even all that unusual.
A sizeable number of both boys and girls engage in prepubescent masturbation.
I accidentally walked in on her in the bathtub the other night to find her stretched out in the tub, relaxing and the water jetting from the faucet was hitting her vulva.
When she realized I had seen what she was doing she simply just grinned at me and stated, "This feels great, Mom! " She now comes to me and ask me if she can watch certain videos (basically "chick flicks") "in private." She seems very comfortable with her newfound adventures, but I am just dying.