Astronomers decided to look for partially constructed Dyson spheres and other megastructures around stars. They determined that half-built Dyson spheres or megastructures would be easy to see with our telescopes. They made a fairly comprehensive search and found seven candidate stars. The candidate stars are all white dwarfs. They also eliminated stars where other astrophysical reasons could confuse...

The best ways to search for extraterrestrial intelligence is to theorize what should be easy to see with our instruments and then to try to look for those signatures. The Milky Way galaxy contains between 100 and 400 billion stars, and at least as many planets. If aliens tried what we have tried so far then they would not detect our civilization.