The corporate systems for this (usually) operate by proxying all HTTP traffic, so any sites which don't play nicely with a HTTP proxy are affected. I've seen "i

The corporate systems for this (usually) operate by proxying all HTTP traffic, so any sites which don't play nicely with a HTTP proxy are affected. I've seen "interesting" problems with some more esoteric HTTP 1.1 features and all sorts of things with streaming sites. You're probably right that this system isn't proxying everything, so its impact would be a lot lower. It all depends on what layer it tries to operate, which we don't really know. I'd love to see an investigation from someone on TalkTalk.