Got the same message today, with the number 265-407-5722 spoofed on caller ID. Since I know the IRS contacts taxpayers via US mail and not by telephone, I was not fooled by this. The thieves are counting on people panicking when they think they're in trouble with the IRS. The Indian/Pakistani scammers used a robotic voice in the message left on my answering machine to disguise the fact that they're overseas. Plus I don't owe any back taxes anyway, so the IRS has no reason to contact me at all.
I got this today, the message saying it was a final notice from the IRS. When I called, I was transferred back and forth to several people claiming to be IRS agents, threatening a lawsuit, saying I owed the over $4,000. Then they asked me if I would like to "resolve this out of court," and asked me if I had the money on hand to pay them. When I started asking questions, they hung up.
I just received a message from this number also stating they had been trying to get a hold of me and this is the final notice that the IRS is filing a lawsuit against me so I better call back ASAP. I know that the IRS contacts people via US Mail and also would never leave an automated machine message if they were really coming after you. Thank you to the people who posted the link to the IRS website telling about this.