Collect as much data as possible on them and use it to shadow ban them, or outright ban them. Blacklist their IPs, devices, etc. You can even blacklist their country temporarily if possible. For DDOS, etc you could look at putting Cloudflare in front of your services. And make sure you rate limit everything.
>We have received massive entries in our database from multiple attackers.
Review all your validation code. If this shouldn't be possible, but your code let it through, it's something you should be validating but are not.
>We have received massive entries in our database from multiple attackers.
Review all your validation code. If this shouldn't be possible, but your code let it through, it's something you should be validating but are not.