Should my friend be worried?

[Chris T. B.]

A good friend of mine was on her computer, watching porn, and a notice came up that said this porn is illegal and you could be fined up to $100,000, with an FBI case, if she didn't pay $300 within the next 24 hours. When she first told me, I told her it was just a scam and that she should disregard it. Then she sent me a picture of what the notice looked like, and it looked pretty legit. Is this a scam, or is it real? Again, basically a summary of what the notice said was that this porn illegal and if she did not pay $300 within the next 24 hours, she would be under an FBI investigation. Scam or real?