The SNR to Mars is not great at the best of times. We no longer radiate a great deal of high-power analog signals, because those are not efficient. Space is noisy, digital signals look very much like noise, and radiating to space is not usually the most efficient thing to do if you can avoid it. Our chances of detecting our own planet even from the nearest star would be pretty minimal. Perhaps someone might be able to explain to me why we postulate being able to detect extrasolar aliens.
A Dyson swarm essentially attempts to completely surround a star with solar panels. Infrared wavelengths would then be uncontrollably radiated out into space by the overheating solar panels.
Yes, I'm aware. How many of those do you think you could hide in a ten-light-year circle around Earth, and how long do you think it would be before we were able to find them? To a first approximation, the only things that we can see at stellar scales are stars, and all of the discussions on this topic seem to revolve around detecting radio transmissions. This page[0] gives pretty pessimistic numbers for the maximum SNR to Mars. There seems to be some massive disconnect between what people are looking for and what we are currently emitting, or what we might expect an advanced species to be emitting. And my assumption in these cases is that it's substantially more likely that I am a fool and missing something important rather than that everyone else is.
