I have a wireless modem that I use for data. Today I noticed it was massively overheating and my computer was running unusually hot.

Then I got a message from my provider that I was almost a gigabyte over my limit.

However I did not use much data recently. Somehow my computer has used several gigabytes yesterday and today when my actual usage was well under 10% of that.

I imagine it is some kind of hack but are there any ideas on what else it might be?

I've been using the same wireless modem for about 6 months. There are no computer users within range of the modem besides me.