I was 100% sure that it was a scam as I deal with this in the business world a lot. Although I didn't realize how unnerving it would be to get one personally. I can't image how it affects older people.
I received a phone call from phone number, instructed to call back the same phone number and ask for "exchange 105". Very broken english and when asked, said they meant extension. I called the number and asked for ext 105, sounded like very same voice (I asked for a name and was told it was Dwayne Maguire) that called and told me that they need my lawyer to call them. I asked why I would need a lawyer and they said that I filed my 2008 taxes incorrectly. I told them that the IRS would contact me, not the US Department of Treasury with a letter to straighten out and then I was told that I would be arrested and put in jail for six months. As I again asked why I needed a lawyer as I believed this to be a scam, they hung up on me.