Not the FBI, but rather Scammers.
Here’s a video somebody made after they got the same message about their iCloud. He called Apple directly.
https://www.youtube.com/watch?v=L9BxsIdTol4
Great piece bud lots of good stuff here,happens to many of us as well.From the link:..........
“Ransomware – malicious software that encrypts your files and then demands payment to unlock them – has become a major scourge of the Windows world.
Mac users just had their first brush with such threats last week, with the appearance of the KeRanger ransomware. However, shortly before KeRanger, I encountered a ransomware event in the Mac world far worse than anything seen for Windows.
This hack seems to have turned an iMac into an expensive paperweight.
A woman named Ericka contacted me, telling me that her Mac was locked by ransomware. At first, I thought this might be one of countless web-based scams out there, pretending to be ransomware, but easy to get rid of.
However, there was an added wrinkle: Ericka said her computer was asking for a six-digit code, and that a Russian hacker was asking for payment in exchange for the code. This sounded like more than a simple scam pop-up.
From the screenshots she sent me, it soon became clear what had happened. The hacker had somehow gotten access to Ericka’s iCloud account.
Using this, he was able to remotely lock her computer using iCloud’s Find My Mac feature, with a ransom message displayed on the screen. (For some reason, the iPhone did not actually end up locked, but displayed the same message.)
IMG_2107The message read: “Contact me: hblackhat(at)mail.ru All your conversation sms+mail, bank, computer files, contacts, photos. I will public + send to your contacts.”
She also received an e-mail message, in similarly broken English, from her own iCloud address. The message said he had access to all her bank accounts, personal information, etc, and would publish it if she didn’t respond within 24 hours”...............
iCloud solution: don’t use it.