well, thats interesting. first, lets make sure your firewall is on
then, it might be interesting to look at the logs, so youll need to enable logging,
sudo ufw enable
sudo ufw default deny
soo, actually theres a lot od different thing which could be going on. Do you get the same huge amount of traffic independent of the network you are on? A bad network port can generate tons of packet errors. Alternatively, you may be receiving broadcast and synch packets from other computers. And if some user on you network has been hacked, they they might be sending everyone a ton of packets.
sudo ufw logging on
to see what your computer is sending doing type:
there you'll see your active connections
sudo netstat -anp |less
alternatively you could try using wire-shark to capture and analyze your packet traffic.
another nice traffic monitor is iptraf you can sudo apt-get install it then use
to get an idea whats coming and whats going on your system.
give that a try, see what you can find and get back to us.