They are saying that they're from the IRS, and saying everything the TV reports say the IRS doesn't do: threaten with arrest, and urge to call back 'right away'. This is probably illegal.
automated call from the irs stating a legal notice has been filed against me for tax fraud and case is registered in Federal Claims Court. I'm not that gullible. The IRS sends letters and I haven't committed any fraud so this is bogus.