John got a pop-up for the FBI MoneyPak scam. Leo says that's exactly what it is. The FBI doesn't sell a get out of jail free card for the cost of a MoneyPak card. Hackers, however, are making billions on it. Not only are they making money, they've locked up his computer as well.
Leo says it's ransomware and he can rid of it. They use a trojan called RansomLock that will lock down the machine until he would send them money. So he should make sure his operating system is updated. It may be a virus that came through Flash, Java or a PDF file that launched Adobe Reader and installed it.
Bleeping Computer has a solution that could help, but Leo says it's only going to work in limited situations. So, the only real way to get rid of it is to backup his data, format the hard drive, and reinstall Windows from a known good source.