Same Here. vm stated someone had filed a lawsuit against me. I called the phone number and it just rang.

Called twice in one day.  Same message as everyone else re:lawsuit.  Did not call back.

I received the same call twice today claiming the IRS is filing  a lawsuit against me.

while doing research on internet, I found this article :
......The Treasury Inspector General for Tax Administration has received reports of about 290,000 fraudulent contacts made since October 2013. The TIGTA is aware of nearly 3,000 victims who have collectively paid more than $14 million as a result of scams in which individuals make unsolicited calls to taxpayers fraudulently claiming to be IRS officials and demanding that they send them cash via prepaid debit cards.
http://www.cnbc.com/2015/10/28/guess-what-thats-not-the-irs-calling.html

I received two calls today from this number informing me of the same, that the IRS has filed a lawsuit against me, and to call them back. I have experienced the same as many of you that called back and found that the line does nothing but ring.

I have filed and incident with TIGTA
https://www.treasury.gov/tigta/contact_report_scam.shtml