Hi @Gustavo Castanheira?,
We have an extensive Google Cloud Dataprep security FAQ at this link: https://www.trifacta.com/security/google-cloud-dataprep/
I would encourage you to share this material with the source owners. Data always remains in a customer's Google Cloud project, and is never persisted outside of the customer environment.
Does this help? Let me know if there is any additional information that would be useful for your data source owners, and we can enhance the FAQ document as needed.