I am sure that I'm not the first one to tell you this, but you can't believe everything you read on the Internet these days 😉
Case in point...I've seen a number of sources claim that custom HTTP modules are not supported in Microsoft Office SharePoint Server (MOSS) 2007 and Windows SharePoint Services (WSS) v3.
These statements make it sound like if you add your own custom processing to the pipeline of each page request, you will instantly teleport your Production SharePoint farm into that vast wasteland we generally refer to as "Unsupported" -- where your support calls to Microsoft will be summarily terminated shortly after getting your Service Request (SRX) number.
Not so -- at least in this particular case.
Thank goodness, at least for my sake, because I've worked on a number of MCS (Microsoft Consulting Services) projects where we've delivered custom HTTP modules. It's always a little scary that something we deliver as part of an MCS engagement will later be deemed "unsupported."
In general, we are very good about knowing what is -- and is not -- supported, but there's always a chance that something "creative" we do in order to satisfy the business requirements for our customers will later be considered a problem by Microsoft Customer Service and Support (CSS).
There are, in fact, lots of things you can do with SharePoint that will thrust you into the dreaded "unsupported" category, but a custom HTTP module isn't one of them.
How can I say this with such conviction? Well, yesterday I came across the following on MSDN:
A HTTP module assembly can be installed in the Web application’s \bin directory or in the global assembly cache.
Because an HTTP module is always called as part of the page processing pipeline, a poorly designed or faulty module can have a detrimental effect on performance or perceived stability of the environment. Thoroughly test each module for performance before deploying it.
If you want to see it for yourself, you can go straight to the source:
Obviously you want to be very cautious about using custom HTTP modules, but there are definitely scenarios where this is a good approach.