An important part of many Web applications is the ability to identify users and control access to resources. The act of determining the identity of the requesting entity is known as authentication. Generally, the user must present credentials, such as a name/password pair in order to be authenticated. Once an authenticated identity is available, it must be determined whether that identity can access a given resource. This process is known as authorization. ASP.NET works in conjunction with IIS to provide authentication and authorization services to applications.

An important feature of COM objects is the ability to control the identity under which COM object code is executed. When a COM object executes code with the identity of the requesting entity, this is known as impersonation. ASP.NET Framework applications can optionally choose to impersonate requests.

Some applications also want to be able to dynamically tailor content, based on the requesting identity or based on a set of roles that a requesting identity belongs to. ASP.NET Framework applications can dynamically check whether the current requesting identity participates in a particular role. For example, an application might want to check to see whether the current user belongs to the manager's role, in order to conditionally generate content for managers.