Security Aspects for Web Services 
Web services use the user administration and authentication mechanisms provided by the SAP NetWeaver platform, in particular those of the SAP NetWeaver Application Java. For this reason, the security recommendations and guidelines for user administration and authentication apply also to Web Services. They are described in the Java Security Guide of the SAP NetWeaver application server.
For more information: User Administration and Authentication
The technical system landscape and communication for Web services is described at design time and also which authorizations you need for Web services.
If you want to publish functions as Web services, check the possible input values.
You can make security settings for the service provider and service consumer for runtime.
SAP Enterprise Services Explorer for Microsoft .NET is an Add-In for Microsoft Visual Studio.
For more information: Security Aspects of SAP Enterprise Services Explorer for Microsoft