Hi
How can I find out where (by site or whatever) my data disappears to?
We've started blowing our data cap and can't work out why or where it's going.  We've been satisfied with 20GB for ages but started blowing that too soon and too frequently so cranked to 50.  Two weeks into the month and we've blown 75% of that already.
Spoken to the ISP (Slingshot) who can tell us WHEN it's being used but not WHERE.  They sent us a table of usage by the hour and we found gigs consumed when we're sure we weren't even in the house and gear likely turned off.
Starting to get nervous of maliciousness ... I've changed the WiFi password and blown away & re-installed from scratch 2 of the 5 PCs - others in the queue.  That hasn't seemed to make any difference so far.
Our inventory is:

• Desktop PC (Win7 Ult)
• 4 x laptops (Win7 Ult)
• 2 x iPads
• 3 x iPhones

OK - there's a bit going on here, but that inventory hasn't changed recently but data usage has - dramatically!

If the ISP can't, is there some way we can find out WHERE big lumps of data are going ourselves? Somewhere in the modem or Router?  Or, perhaps better, some app that can log this stuff in a vaguely user-friendly way?
Any clues or suggestions out there?