I have no idea what the machine is doing. I don't even have a hypothesis as to what it's doing. Yet I have recognized the machine as the product of an alien intelligence.

Are beaches the product of an alien intelligence? Some of them are - the ones artificially constructed and maintained by humans. What about the 'naturally-occurring' ones, constructed and maintained by entropy? Are they evidence for intelligence? Those grains of sand don't wear down, and they're often close to spherical. Would a visiting UFO pause in awe to recognize beaches as machines with unknown purposes?