Yes, please install McAfee Web Reporter then you can identify which computer/user account is responsible for it. All web traffic will be shown in reporter with great details of sites and bandwidth consumed.
Thx. Without Web Reporter or CSR you can see that in the Feedback-File "running-mwg-core.txt" or command "/opt/mwg/bin/mwg-core -S connections". Command or Feedback-File must create at time when traffic is there.