[gus_massa]

I strongly suspect it's a natural source, like the little green men sources https://en.wikipedia.org/wiki/Pulsar

Anyway, we can try to detect strange signals, like signals with a narrow bandwidth, some regularity, like repetitions, and some parts that looks like random, like the letters in a foreign language you don't understand.

For examples, see the image in this article and ignore all the text: "The sound of the dialup, pictured" https://www.windytan.com/2012/11/the-sound-of-dialup-picture... HN discussions https://news.ycombinator.com/item?id=15635144 (675 points | Nov 6, 2017 | 108 comments) and https://news.ycombinator.com/item?id=9171514 (174 points | March 9, 2015 | 35 comments)

Even if you don't understand what it's happening, there is clearly something weird and not natural.