[Koha] DDoS attack on memcached

[Mark Alexander]

Apparently, a bug in memcached (which we use in Koha) causes it to be
used an intermediary in a DDoS attack:

https://arstechnica.com/information-technology/2018/02/in-the-wild-ddoses-use-new-way-to-achieve-unthinkable-sizes/

I'm not an expert on this kind of thing by any means, but judging
from this:

  https://github.com/memcached/memcached/wiki/ReleaseNotes156

It seems that we can disable the attack by preventing memcached from
listening on a UDP port.  I was able to do this by adding the
following lines to /etc/memcached.conf:

  # Disable UDP
  -U 0

Then restarted memcached and apache2.

My questions for the experts: Is this the correct approach?  Is it even necessary?
Is there more we should do?