What is FBI protocol for informing you you are going to be charged with a cyber crime?
I think I may be being scammed.
If your computer is locked up with a big FBI warning screen of some sort, it's a computer virus. You need to get a really good virus removal program and run it so you can get rid of it. http://www.fbi.gov/news/stories/2012/august/new-internet-scam and https://support.norton.com/sp/en/us/home/current/solutions/v71075396_EndUserProfile_en_us
Sephira is right. The FBI doesn't bother sending warnings. If it was the FBI they would be knocking at your door instead of sending you a warning.
The protocol is a couple of agents knock on your door. They NEVER notify you thru your computer!
They notify as they arrest you. NEVER will they let you know ahead of time. See Sephira's answer for what to do.