I have written an ISAPI filter for IIS 5.x and 6.0 which intercepts responses from the web server. I have noticed that POST responses processed by ASP.NET (aspnet_filter.dll) do not invoke my filter's OnSendRawData() handler. I am assuming that ASP.NET is writing the response directly to the client via WriteClient() and that I therefore cannot intercept the response body. Can anyone on the IIS/ASP.NET teams or otherwise clarify this behaviour?