Internet Connectivity

We had several machines start spewing huge amounts of data causing our
pipe to the public Internet to stop. We had no traffic coming in or out
of the campus. We're unsure of whether it's virus related, but wanted
to inquire if anyone else has heard of or came across something similar.
It appears to be an DDOS attack, but, originating from the inside. This
started last night at about 10pm EST.