If you were "hacked" (ie password reuse), the attacker can just relimit this.
Enabling MFA, restricting intra/inter-VPC access, removing hard-coding credentials from configuration files/source etc., switching to SSO/removing user accounts with passwords, creating and applying restricted IAM roles, and applying those reduced privileges to EC2/ECS/EKS instances are all things that and should be done as soon as possible. (Non-exhaustive, but illustrative list)