NTP attack

Yep we got bit by this one. It brought our network to its knees. Fortunately the fix was easy. First, to stop the attack we turned off ntp temporarily:

service ntp stop

Then we added this to our /etc/ntp.conf file:

Disable monitor
Restrict -4 default kod notrap nomodify nopeer noquery

Then we started ntp:

service ntp start

The system returned to normal.