These guys write Mac malware for a living and use nefarious tactics to fool users into installing it, while making it really hard to uninstall. I've seen it on the Mac of many less technically inclined people.

Things like: “your Mac has been infected, click here” while the user is downloading some torrent or watching porn. Faking the system's dialog boxes, using chatbots “is your Mac slow?”, etc.

I'm amazed Apple hasn't banned them from the Mac App Store. I don't know how these people sleep at night.