Broadband cost increase

Got a shock today to find that our broadband usage had suddenly increased from 1 GB a month to almost 1GB a day. Enquiries with Telstraclear seem to suggest its been my avid learning with this blog set up (and particularly the trying to upload a video that is responsible) anyway we've disabled the wireless part just in case it wasn't protected properly (I don't think it was at all & maybe someone clever had got into it)and we'll see if that improves things.