QTOBDNS - disk busy percent

One night this week our System i went from averaging 0-3% busy on all disks (which is normal) to 30-50% busy and stayed there. This destroyed our response time, making the system barely usable.

For 2½ days we tried everything we could think of, all to no avail. Our CPU utilization was fine, our disk space was fine, there were no 'runaway' jobs, etc. Our disks were simply getting hammered. We brought in our BP and he adjusted our memory allocation, moving memory from two unused partitions, and that helped tremendously. Our page faulting was within normal expectations, so why would additional memory help?

But here's my real question. While searching for the culprit, I ran across a system (QTCP) job, QTOBDNS. I was surprised at how much CPU it was taking so I checked its job log. There were hundreds (if not thousands) of entries that really concern me. Example...:
mixpanel.com
aniview.com
d.turn.com
brealtime.com
akamaiedge.com
rubiconproject.com
googleapis.com
taboola.com
(you get the idea)

I have a basic understanding of what a DNS does but this really seems strange. Could this job be the source of our original problem? And here's the question I hate to ask, but need to: is it possible we've been hacked?

We're currently on 7.2. And no, we're not up-to-date on PTFs.

Thanks in advance for any thoughts on this.

~TA~