Wireshark-users: [Wireshark-users] Finding an intruder
From: Steve Matzura <sm@xxxxxxxxxxxxxx>
Date: Wed, 14 Dec 2016 21:06:55 -0500
New to the list, been using some version of the Shark way back to
Ethernim days, so I'm familiar with its capabilities. It's become
quite sophisticated lately, hence the following problem description
and question.

A friend has a cable Internet provider with data caps. Lately, he's
been getting nastygrams from them that he's exceeded those caps, and
it's only two weeks into his billing month. Something somewhere is
sending and receiving tremendous amounts of data, and I've been taksed
to find out what's doing it. So, should I just run Wireshark and
capture everything, collect some ridiculous amount of data and
hand-analyze it, or might there be a convenient filter out there in
Wireshark cyberspace land that could help me narrow the field and nail
the culprit? Antivirus, antimailware, antispyware scans all come up
clean and green, the DHCP client list on the router has no unknown
devices in it, we're stumped, so I'm turning to the best network
monitoring tool I know to help me dig this one out.

Thanks in advance.