The Service Account is an account you create on premises and sync into Azure AD. It requires the rights as explained in this article but these are standard and should not be a problem in most environments.
- Service requires Log on locally right and Log on as a service right (the second will be given during scanner service install)
- Service account requires Read permissions to each repository for discovery and Read/Write permissions for classification/protection
Additional information about the Service Account and advanced permissions can be found at https://docs.microsoft.com/en-us/azure/information-protection/deploy-aip-scanner#prerequisites-for-the-azure-information-protection-scanner and https://docs.microsoft.com/en-us/azure/information-protection/deploy-aip-scanner#deploying-the-scanner-with-alternative-configurations