Physics pretty much dictates a tool biulding civilization will be using radio.
at one or two particular wavelengths,
We are looking at billions.
and at sufficient strength to be detected by Arecibo, etc.
Going to narrowband searches up the odds a bit. :-)
Unless the other guys are transmitting spread spectrum, with many "circuits" using the same frequencies but different spreading codes.
Of course there aren't that many good codes. Perhaps we should try some of them and look for a wider band width signal. Maybe we could detect their version of GPS.
Be that as it may, my home PC is right now looking for ET using SETI@Home