SSRS Unattended Execution account

Reporting Services provides a special account that is used for unattended report processing and for sending connection requests across the network. The account is used in the following ways:

·         Send connection requests over the network for reports that use database authentication, or connect to external report data sources that do not require or use authentication. For more information, see Specify Credential and Connection Information for Report Data Sources in SQL Server Books Online.

·         Retrieve external image files that are used in report. If you want to use an image file and the file cannot be accessed through Anonymous access, you can configure the unattended report processing account and grant the account permission to access the file.

http://msdn.microsoft.com/en-us/library/ms156302.aspx

Credentials are encrypted in rsreport config file.