I called the regional FBI office and it certainly is a scam.  The FBI is aware of it.  They said "Don't get involved in any way.  Just shred the letter and check".  So don't respond to them or try to cash it.  I don't know how they would get you from the check, but access to your bank account comes to mind.  Who knows.  I also have been getting a flood of emails from "attorneys" from all over the globe who have millions they need me to help them get rid of.  Right.  Who needs a stimulus with all this free money?