It leaves a computerized message of an IRS lawsuit.  When you call back, you have an Indian guy who is very rude and vulgar and hangs up on you, and masks his voice when you call him again.  When you tell him the jig is up, he gets vulgar again and even makes threats.

He does not seem "scared" to stay on the line as long as you challenge him for.  He has that "bring it on" attitude even if you pretend to be FBI or some other intelligence agency.

It was fun trying to push his buttons, but he obviously got my number from some fraudulent person, and so I'm a little peeved at how periodically I get similar calls like this.