How to run your service under a specific identity
Jason Taylor, Prashant Bansode, Carlos Farre, Madhu Sundararajan, Steve Gregersen
If your service is hosted in IIS 6.0, use IIS Manager to create an application pool running as a specific identity. Use IIS Manager to assign your WCF Service to that application pool.
If your service is hosted in Windows Service, configure the Windows Service to run using the particular identity, the WCF service will run under the security context of the Windows Service.