Hello someone is trying to make multiple signups on my website with different IP what could be the easy way to prevent this . I am using aws stack for website hosting
You cannot simply distinguish them because all requests are legitimate, or at least the attacker can make it look legitimate (e.g. innocent-looking user agents, etc.).
One common practice is to employ Captcha/reCaptcha so that bots can be blocked, but still it wouldn't work if the person is dedicated enough to solve them manually.