4-moduled Avalon B3 generated 27 gb of outgoing traffic per 24 hours? can this be true?
Not likely
Here are 8 Avalons (6 x 3 + 2 x 4 modules) running:

One machine uses about 7 MB / day worth of trafic
Thank you for detailed answer. Here's what I've got: 2Gb for just 5h 35m:

My Avalon is hosted in the datacenter and they are asking me to pay bills for this gigabytes (total 143 Gb for more than 1 month).
Firmware was taken from
http://ck.kolivas.org/apps/cgminer/avalon/20130821/wow that's a lot of data
Uptime: 32d 13h 53m 30s
RX: 1.15 GB (11060428 Pkts.)
TX: 2.35 GB (18433190 Pkts.)
and that's been running flat out for over a month now
a tcpdump on your router will tell you what is going on. Have in mind it might be faulty Ethernet interface also