The easiest way is to look at what comes up in /new. You’ll see copycat subreddits pop up and suddenly be full of reposts filled with accounts saying bland replies. Usually mundane things like copies of r/aww. Click on the accounts themselves and look at their activity. It’s subreddits of bots replying to bots. They do that until they reach a certain maturity then likely get sold to advertisers and propagandists