Filter NTP traffic by packet size?

Robert Drake rdrake at
Wed Feb 26 22:48:59 UTC 2014

On 2/26/2014 5:33 PM, Valdis.Kletnieks at wrote:
> On Wed, 26 Feb 2014 11:44:55 -0600, Brandon Galbraith said:
>> Blocking chargen at the edge doesn't seem to be outside of the realm of
>> possibilities.
> What systems are (a) still have chargen enabled and (b) common enough to make
> it a viable DDoS vector?  Just wondering if I need to go around and find
> users of mine that need to be smacked around with a large trout....
I would do it.  I scanned all my public and private networks and found a 
few.  I've added it to our customer acls to stop it.  There were also a 
couple of internal routers that someone had turned or left it on that 
were missed.  Those are now fixed.

nmap -T4 -oG chargen_scan.txt -sS -sU -p 19 <your netblocks here>

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