The connect I was looking for was Numbers Stations. As many of you identified, the three numbers were VoIP numbers that, when called, read out a series of numbers to the caller. This prank, called Project Evil, was perpetrated via CraigsList by a group of hackers to find out the strength of the online crypto community. (Numbers Stations, as the wikipedia article will tell you, were used by various spooks during the cold war to transmit encoded information to their headquarters. )