QUESTION

If I have logs stored in an S3 bucket, and I configure that S3 bucket as a Data Transport in Panther, will Panther ingest the logs that already existed? 

ANSWER

No, Panther will only pick up new logs added to the S3 bucket after you configured it as a Data Transport. 

While setting up your S3 source in Panther, it is possible to generate one or more schemas by reading historical S3 data, but that historical data is not onboarded to Panther.