Is it possible to use both packet level and application level filtering with in the same program ie. inspect packet using winPKfilter then a LSP/TDI filter?
Does your company provide a application level filter?
We provide localhost monitor API, which is TDI filter for Windows NT/2000/XP/2003. LSP sample is avalaible as a part of MSDN. Simple TDI filter for Windows 9x can be found in the VTOOLSD samples (from Compuware).