Why are third-party domains redirecting to my site?

Question

DDoS Protection

The other day there was a DDoS attack on my site, in total the server (on one IP). Connected a new IP, all sites are working. But after that, excessive activity began to be observed on one of my sites, about 100 domains redirect to my site by metric. Can a search engine perceive these pages as duplicates, and in general, who benefits from it? How to stop the negative consequences of this?