You can read more about DOS attacks here: https://en.wikipedia.org/wiki/Denial-of-service_attack
More about open DNS resovler exploitation for DDOS attack (DNS reflection) you can read here:
https://www.cert.be/pro/docs/dns-amplification-attacks-and-open-dns-resolvers
Default Kloxo control panel installation leaves DNS service not secured and open for exploitation for this kind of attacks by the remote attackers!
To prevent network abuse and involving your server in DDOS/FLOOD attacks, you HAVE to disable recursion in Kloxo DNS service:
1) Login in your server shell command prompt as root and open NAMED DNS service configuration file located at /var/named/chroot/etc/named.conf with your prefered editor:
For example you can run:
nano -w /var/named/chroot/etc/named.conf
2) Add the following text at the end of this file:
options {3) Restart NAMED service.
recursion no;
};
