They'll only affect your member read ratio if they are members. So if they don't have a star, you can relax. If they do have a star and they're not staying on your stories for 30 seconds, then they'll show as a view, not a read, and will bring down your read ratio, which affects earnings. You can't know what they're doing, but can only take an educated guess based on number of comments, number of reads, and making a judgement on who you believe is genuine.