I have been getting these calls for couple of days. One of the numbers was 202-599-9602. The other one was 202-506-8153
In both instances a recorded voice left a message similar to what MND has paraphrased in the comments. I had received couple of calls about 2 months back as well. At that time it was a human voice (unlike the recording this time) with a thick accent. I spoke to the person and asked him a few questions related to taxes and he fumbled in his answers and said I was wasting his time :). I had then reported the call on the IRS website.
I unknowingly returned the missed call, and they claimed they were part of a Federal Crime Authority wanted to know information about my location and computer system. I refused to provide any information and in an upset tone he told me not to call them back again. Hopefully they will do the same.