Originally Posted by horrorfan
Later that day I went to the library and that's when it went up 70MB in 10 minutes, though it stabilised and went pretty much as normal for the next 1.5-2 hours.
This might not necessarily be anything malicious at all and could actually be something simple like Windows Update just downloading updates (assuming you have set it to automatic). The pattern of the downloading would match that as well and 70MB isn't necessarily that much if multiple updates were downloaded at the same time. I would check Windows Update and see whether any updates were downloaded/installed around the time you experienced the higher data usage.