ping flood /mach_kernel what is this?

I am receiving the following message:

Symantec Notification

X vulnerability BLOCKED

when: Apr 3, 2016, 10:38:01 PM

From: [ip adderss]

Attack Name: Ping Flood

Application: /mach_kernel

What does this mean and what can I do to "fix" this as I get this message 15-20 times in 2 hours.

THANKS!