Can you explain what an authorization filter is in the context of web applications?

Authorization filter in web applications is a component that intercepts HTTP requests and checks whether the user has the necessary permissions to access the requested resource.

It operates before the request reaches the controller or handler and can:

• Check the presence and validity of the user's token or session.
• Determine whether access to a specific URL or action is allowed.
• Redirect unauthorized users to the login page or display an error.

In ASP.NET, for example, the authorization filter is implemented via the IAuthorizationFilter interface or attributes that can be applied to controllers and methods:

public class CustomAuthorizationFilter : IAuthorizationFilter
{
    public void OnAuthorization(AuthorizationFilterContext context)
    {
        if (!context.HttpContext.User.Identity.IsAuthenticated)
        {
            context.Result = new UnauthorizedResult();
        }
    }
}

Thus, the authorization filter provides centralized and reusable access control logic.