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Vulnerability Assessment Details

Usable remote name server

Vulnerability Assessment Summary
Acertains if the remote name server allows recursive queries

Detailed Explanation for this Vulnerability Assessment

Summary :

The remote name server permits recursive queries to be performed
by the host running nessusd.


Description :

It is possible to query the remote name server for third party names.

If this is your internal nameserver, then forget this warning.

If you are probing a remote nameserver, then it permits anyone
to use it to resolve third parties names (such as www.nessus.org).
This permits hackers to do cache poisoning attacks against this
nameserver.

If the host permits these recursive queries via UDP,
then the host can be used to 'bounce' Denial of Service attacks
against another network or system.

See also :

http://www.cert.org/advisories/CA-1997-22.html

Solution :

Restrict recursive queries to the hosts that should
use this nameserver (such as those of the LAN connected to it).

If you are using bind 8, you can do this by using the instruction
'permit-recursion' in the 'options' section of your named.conf

If you are using bind 9, you can define a grouping of internal addresses
using the 'acl' command

Then, within the options block, you can explicitly state:
'permit-recursion { hosts_defined_in_acl }'

For more info on Bind 9 administration (to include recursion), see:
http://www.nominum.com/content/documents/bind9arm.pdf

If you are using another name server, consult its documentation.

Network Security Threat Level:

Medium / CVSS Base Score : 4
(AV:R/AC:L/Au:NR/C:N/A:N/I:P/B:I)

Networks Security ID: 136, 678

Vulnerability Assessment Copyright: This script is Copyright (C) 2005 Tenable Network Security

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