To make a custom response message:
- Go to the AWS WAF console in your respective AWS Region.
- Through the navigation pane, select Web ACLs, and then select your web access control list (web ACL).
- Click on Custom response bodies, and then select Create custom response body.
- For the Response body object name, enter whatever name you like.
- For the Content type, click on Plain text.
- In the Response body, mention your response message, and then select Save.