I Read Your Mail Headers

Nobody comments on the most obvious feature of the Interception Modernisation Programme -- the scheme to put intelligent sniffers in every ISP, funnelling anything GCHQ wants back to Cheltenham.

It's totally unauthenticated. Sniffers are purely at the network level. It identifies IP addresses, but not users. Without getting into the great "IP is [not] Personally Identifiable Data" debate, it seems pretty clear that this material will have to work pretty hard to prosecute anyone.

So it's just intelligence gathering? Pure snooping?