quick fix for a server administrator.
my server appears to have been used in a DNS amplification/reflection attack, we need to apply a patch/ fix to prevent this from reoccuring.
Upto you to check whats needed and apply the fix, maybe we just need to disable recursion or limit it to trusted/known clients (recursion no; and allow-query-cache {none;};). maybe its something more.
for your info: we have 'ISPCONFIG Version: 2.2.27' installed and are using the 'DNS BIND server'