I was looking at maps when I noticed that octopus seems to always be depicted as the enemy. During cold war posters I saw both sides representing the other as an octopus. I also saw this occur with Germany during the world wars. A final case I found was England as one during African colonization.
Its tentacles, signifying it reach. Perhaps there's more to the image but the aspect of the tentacle that surround and swallow is what stands out for me. We had a 1980s television show about the Sicilian mafia called La Piovra, "The Octopus", with the same imagery, that this organisation can get into anything.