• Sql Recursive Queries

Note: you can skip ahead to fixes.Recently the hosting company ISPrime became the victim of a DNS-based DDoS attack using spoofed source addresses. Some are calling it an amplification attack because the query '. IN NS' is quite small (47 octets) while an upward referral response is a bit larger (256 octets). For some additional information on this attack, see.

OARC members can track this as.One interesting aspect of this attack is that the queries are apparently sent to authoritative nameservers only. In the past we have seen DNS-based attacks bounce queries through open resolvers. Its not clear why this attack is using authoritative nameservers.

Selective Recursion Control Using DNS Server Policies. But as the DNS server is also listening to the external queries, the recursion is also enabled for external clients and the DNS server becomes what is known as an open resolver. Name Resolution Performance of a Recursive Windows DNS Server 2012 R2.

Perhaps because it is easy to get a list of nameservers if you already have a list of domain names and you can be reasonably sure that an authoritative nameserver will give some kind of answer.The attack brings an old debate back into the light: What is an authoriative nameserver's appropriate response to a query that cannot be answered?The configuration and/or implementation of some authoritative nameservers causes them to return an upward referral to the root zone. We recommend against this behavior for a number of reasons:. Upward referrals are generally useless. DiG 9.3.4-P1 @10.0.0.26.

Sql Recursive Queries

Ns; (1 server found);; global options: printcmd;; Got answer:;; -HEADER Eliminating Upward Referrals. Disable recursion on authoritative nameservers with this global option:recursion no;.

If your BIND nameserver is a master for some zones, it needs the root hints to correctly send NOTIFY messages to the slave nameservers. To prevent upward referral responses, you can add this line to the global options:additional-from-cache no;Then, a query such as '. IN NS' should result in a REFUSED response.Alternatively, you can use access controls to accomplish the same thing by denying all queries globally and then allowing queries for each zone. Click to see an example.