Such an http header can be seen with Fiddler:
To prevent that the advertising from the X-AspNet-Version is added to the http header it can be removed via the following steps:
1.) Open the IIS Manager (on the affected Windows 2012 R2 OS)
2.) Select the server
3.) open the "Configuration Editor"
4.) change to "system.web/httpRuntime"
5.) change the "enableVersionHeader" from "True" to "False"
6.) save the configuration
You do not need to restart the Windows OS for this. Once saved it will be active!