XLSX file upload to s3 bucket creates additional enc files

The behavior you're observing with .xlsx files creating additional .enc files when uploaded to an S3 bucket is not a standard or expected behavior for Amazon S3. S3 typically stores files as-is without creating additional files or modifying the original content.

There are a few possibilities that might explain what you're seeing:

1. Encryption: If you have enabled default encryption on your S3 bucket or are using client-side encryption, it's possible that the .enc files are related to the encryption process. However, this would typically apply to all file types, not just .xlsx files.

2. Versioning: If you have versioning enabled on your S3 bucket, you might see multiple versions of the same file. However, these would not appear as separate .enc files.

3. Third-party software: If you're using any third-party software or plugins to manage your S3 uploads, it's possible that this software is creating the additional .enc files for Excel documents.

4. Custom Lambda function: If you have a Lambda function triggered by S3 uploads, it could be creating these additional files for Excel documents.

Given that this behavior is specific to .xlsx files and not observed with .docx or .csv files, it's likely that there's some process or configuration specific to handling Excel files in your setup.

To troubleshoot this issue:

1. Check your bucket configuration for any special rules or triggers related to .xlsx files.
2. Review any custom code or Lambda functions that might be processing uploads.
3. Check if you're using any third-party tools for S3 management that might be causing this behavior.
4. Verify if this behavior occurs when uploading from different sources (e.g., AWS CLI, SDK, or direct console upload).

If you can't identify the cause after these checks, you may want to contact AWS Support for further investigation, as this is not standard S3 behavior.
Sources
Using Amazon S3 from AWS Explorer - AWS Toolkit for Visual Studio