I am creating a .NET REST SOE for ArcGIS Server 10, and I will need to determine if a map service (or image) is secure or not.
Is there a property on a MapService that would tell me this in either ArcObjects or REST?
To check if the service is secured from the GIS Tier, you can use the ArcGIS for Server Admin API.
Query the REST end point is this
If the REST end point returned "esriEveryone", it means it is public. Else it will return the permitted Roles or Group who can access this service.
You can access the Admin API from here, you would need to use the primary administrator or any administrator login.
However, to check if it is secured from the Web-Tier, you can check if protocol is HTTPS or the port being used is 443.