AWS Shield is a managed DDoS protection service that safeguards applications running on AWS. It provides always-on detection and automatic inline mitigations that minimize application downtime and latency. There are two tiers:

• AWS Shield Standard: Automatically protects all AWS customers at no additional cost against common, most frequently occurring network and transport layer DDoS attacks
• AWS Shield Advanced: Provides enhanced DDoS protection for applications running on Amazon EC2, Elastic Load Balancing, Amazon CloudFront, AWS Global Accelerator, and Route 53

Other options explained:

• AWS Firewall Manager: A security management service that allows you to centrally configure and manage firewall rules across your accounts and applications
• Amazon GuardDuty: A threat detection service that continuously monitors for malicious activity and unauthorized behavior
• Amazon Inspector: An automated security assessment service that helps improve the security and compliance of applications deployed on AWS