i had this happen a while back when verizon just got on the dsl bandwagon. i didn't even notice it till i first installed zonealarm into my new system. for some reason, verizon was connecting with more than 1 program to the internet, but i couldn't pinpoint which one was sending/receiving all the info. so i simply started blocking them 1 by one till i found out which ones i needed to keep my connection alive & which were unnecessary. problem solved.
like other people suggested, probably something or other updating/monitoring. use zonealarm to find your culprit.