I got a scary call today from persons purporting to be from IRS.  They said that they had sent a letter last Jan. saying that a random audit showed that I had intentionally reported miscalculations and owed some $3,500 for 2008-2012.  The address to which they first said they sent it had the wrong zip code; when they "got my file"--NOT pulled it up on computer--after I had told them the correct one, they said they made a mistake and that they had sent it to the right one.  Then they said that a law suit was being filed with 4 charges under IRS Code #6331 with threats to garner ALL my assets, deport me if I were a "member" of another country, and issue within 3 hours a warrant for my arrest with imprisonment for up to 6 months.  I asked them to resend the letter with all the details so I could tend to it, and they said that they couldn't.  When I said that I wanted to submit it to my CPA, they said that wasn't possible and that I had to have a criminal lawyer and appear in court.  They kept asking if I had any intention to resolve the issue.  I said "yes" various times but that I could not get copies of the letter or any details about what was owed and why.  They kept saying that I wasn't answering the question, getting more and more aggressive and not allowing me to respond or ask questions.  I finally hung up on them.
I have talked to my CPA and a tax lawyer, and they were both initially concerned and then started laughing!
Red flags:
1.  Both were Indian/Pakistani.  Okay for the first one but not expected of the one to whom I was transferred, "the chief attorney".
2.  The thing about "getting" my file and if I were a "member"--not citizen--of another country.
3.  A lot of noise in the background like a tele-marketing business but also a car honking.  Sorry, IRS has offices in big, air-conditioned buildings...
4.  !!! Contact by phone!!!  IRS does NOT contact people by phone, maybe not even email, for these purposes.
5.  Refusal to send another copy of the letter when I said that I really didn't get the first one.  Said they couldn't and that sending info to the CPA was not allowed.  I would need a criminal lawyer to appear with me in court.
6.  Such drastic consequences for only $3,500 with no second chance.
7.  It was alarming because they had my name, my address (albeit with the wrong zip at first), my phone number, and the first 5 digits of my SS#!  They also said that the case was against me alone and did not include my husband which is curious because we file jointly.  How could they have separated out my information from the combined whole return???!!!
Result:  Apparently this is a Pakistani/Indian scam.  I didn't talk to them long enough to get to where they would offer for me to  send the money or a fee for their lawyer to settle out of court.  Wonder where they would have asked me to send it and to whom?
Watch out!  Hang up on them, and they won't call back, realizing that you have probably figured it out and won't take the bait.
I also have gotten spurious emails from the IRS supposedly and report them.