Securing Twilio webhooks is crucial to prevent malicious or opportunistic third-party requests from reaching your application. Twilio signs all valid webhook requests with an X-Twilio-Signature header, which can be validated by recreating the signature using the request details and auth token. To implement this validation in a Spring application, a custom annotation `@ValidateTwilioSignature` is used to mark methods that require validation, while a `HandlerInterceptor` class checks the signature against the request headers, extracting parameters from the body of the request as needed. This ensures that only valid requests from Twilio reach the application's handler methods, providing an additional layer of security for webhook configurations.