This is an active search. They are looking for things they know they can detect and which—if detected—will provide them with enough certainty that they're looki

This is an active search. They are looking for things they know they can detect and which—if detected—will provide them with enough certainty that they're looking at output from an alien civilization to warrant further investigation. We may stumble upon something novel, like Tabby's Star[0], and ultimately determine it is caused by an alien civilization or not. This sort of passive search is fine; but generally speaking, if aliens do things differently than we do, they will either be invisible to us, or we won't know we're looking at them even if we see them. We don't know enough to have any kind of active search for aliens that aren't like us in some way. Even searches for things like Dyson swarms are informed by speculating about our own needs. [0] - https://en.wikipedia.org/wiki/Tabby%27s_Star https://en.wikipedia.org/wiki/Tabby%27s_Star