Received automated call saying it was google trying to secure my account from a hack. Left a code for me to use. However, I checked and there was no attempt by google to advise me of the hack.
I'm porting my carrier number to my Google voice number. During the verification process Google prompts you to hit a button that says, "Call me." An automated system calls you on the number you want to port to verify it is your number to keep people from fraudulently switching someone's number. There is also a two digit (in my case) number beside the "Call me" button.
When you answer you punch in the two digit number on your keypad.
So, BigA, TheRealSeriously, B-Edwards, et al... this number IS used by Google to verify your info. You don't give them any identity, passwords, etc.... just a random code.
Perhaps the 202-455-8888 number is spoofed by the scammers other people are getting calls from, but the folks who were getting verified by Google, were in fact legit.
Calling your phone number to punch in a verification code is used by many of the more security advanced companies (my 401k company) as a form of two-step verification.
There might be some truth to this. There is a Craig's List scam that involves tricking people into porting their number to a Google Voice number.
https://www.youtube.com/watch?v=l_IFCzd42sQ
https://productforums.google.com/forum/#!topic/voice/KmXQvVot1cA