Amazon Shield is the service name for the inbuilt DDOS protection service that has been running in the background of AWS. AWS have decided to make its existence public and share details on its capabilities and features.
If you already use AWS then you are already taking advantage of Amazon Shield. They provide this service automatically in the background. Its main purpose is to prevent malicious attacks from affecting your running services. In the event of a denial of service attack, Shield uses packet filtering and clever routing to stop malicious traffic from swamping your cloud infrastructure and bringing it down.
This service is great for protecting against most types of attacks for great value (it’s free) however if more advanced protection is required Amazon offers an extended version of shield called AWS Shield Advanced. This offers additional services such as a dashboard for monitoring attacks and the services of the DDOS response team made up of AWS staff to assist you to ensure you environment is safe from attacks and to help mitigate any ongoing attacks. This is a premium service and will appeal to organisations where a DDOS attack could mean significant commercial disruption and loss of business. The advanced Shield service starts at $3000 a month and requires a one year commitment. The pricing of Shield Advanced compares favourably to the costs of most commercial grade DDOS protection.
AWS Shield is battle tested as it was developed to support amazon.com. This follows a trend of AWS releasing features that are based on services they developed internally – such as Amazon Connect.
Standard Shield is more than sufficient for many use cases and eliminates the need to work with a third party to secure your cloud.=
More details here: https://aws.amazon.com/shield/