[conover]

From what I've read, the signals from these probes are so weak that you need large receivers coupled with extremely low temperature electronics to detect them. That puts it out of the reach of everyone except the extremely well funded. In the end, it would be a short list of suspects.

[mturmon]

Yes, you quite literally need one of these to communicate with Voyager:

http://www2.jpl.nasa.gov/files/images/browse/jpl9020ac.gif