HostOnNet Blog

Open DNS servers Fail

Today a clients name servers show following error on dnsreport.
 
Open DNS servers Fail
 
ERROR: One or more of your nameservers reports that it is an open DNS server. This usually means that anyone in the world can query it for domains it is not authoritative for (it is possible that the DNS server advertises that it does recursive lookups when it does not, but that shouldn’t happen). This can cause an excessive load on your DNS server. Also, it is strongly discouraged to have a DNS server be both authoritative for your domain and be recursive (even if it is not open), due to the potential for cache poisoning (with no recursion, there is no cache, and it is impossible to poison it). Also, the bad guys could use your DNS server as part of an attack, by forging their IP address. Problem record(s) are:
 
Server xxx.xxx.xx.xxx reports that it will do recursive lookups. [test]
Server xxx.xxx.xx.xxx reports that it will do recursive lookups. [test]
 
The problem is fixed by adding following to /etc/named.conf and restarting named.
 
recursion no;
allow-recursion { ADD_LIST_OF_YOUR_IP_RANGES_HERE; };

Posted in Uncategorized. Bookmark the permalink.