Looking for Lurkers: Co-orbiters as SETI Observables: https://iopscience.iop.org/article/10.3847/1538-3881/ab3e35/pdf
A recently discovered group of nearby co-orbital objects is an attractive location for extraterrestrial intelligence (ETI) to locate a probe to observe Earth while not being easily seen. These near-Earth objects provide an ideal way to watch our world from a secure natural object. That provides resources an ETI might need: materials, a firm anchor, and concealment. These have been little studied by astronomy and not at all by the Search for Extraterrestrial Intelligence (SETI) or planetary radar observations. I describe the objects found thus far and propose both passive and active observations of them as possible sites for extraterrestrial (ET) probes.