Nis.exe using over 500MB of data a month

Hi I'm running Norton Internet Security on my Windows 8.1 laptop.
I'm using Networx to monitor my data usage, and I've noticed that a program nis.exe (which I'm told is Norton's) is using 500MB to 1000MB every month. The heavy usage only happens over 2 or 3 days a month. I've being using Norton's for 7 or 8 years, and as far as I can tel it only started doing this 3 or 4 months ago. Does anyone know why it is using so much data? Is there any way to cut this down? Thanks.