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cache snooping attacks

Hi All
My astaro DNS settings are the following

1)I am allowing internal network to use DNS
2)I am using openDNS to resolve and not the ISP ones
3)I have multiple static entries (in reverse) 
4)I am using dyndns

After using nessus to test my astaro box on the inside interface (IPS,port scan allowed), I got the following medium vunerability

The remote DNS server responds to queries for third-party domains
that do not have the recursion bit set. 

Explanation
=================
Synopsis

The remote DNS server is vulnerable to cache snooping attacks.

Description
The remote DNS server responds to queries for third-party domains
that do not have the recursion bit set. 

This may allow a remote attacker to determine which domains have
recently been resolved via this name server, and therefore which hosts
have been recently visited. 

For instance, if an attacker was interested in whether your company
utilizes the online services of a particular financial institution,
they would be able to use this attack to build a statistical model
regarding company usage of that financial institution.  Of course, the
attack can also be used to find B2B partners, web-surfing patterns,
external mail servers, and more.

Note: If this is an internal DNS server not accessable to outside
networks, attacks would be limited to the internal network. This
may include employees, consultants and potentially users on
a guest network or WiFi connection if supported.

Solution
Use another DNS software.

See Also
For a much more detailed discussion of the potential risks of allowing
DNS cache information to be queried anonymously, please see:
www.rootsecure.net/.../dns_cache_snooping.pdf

Risk Factor
Medium

CVSS Base Score
 5.0 (CVSS2#AV:N/AC:L/Au:N/C[:P]/I:N/A:N)

Plugin Publication Date: 2004/04/27


How can someone resolve this?


This thread was automatically locked due to age.
Parents
  • This is a bug and should be pursued with support.  A client can request Dns lookuos with or without recursion.  If yhe client does not have the authoritative answer, it should return s pointer about where to look next.  It should not recurse to find the answer.   Spparently UTM is doing recursion even when it is soecifically told not to do so.

  • What has changed in the behavior of "allow-recursion" and "allow-query-cache" gives you the modifications you can make to /var/chroot-bind/etc/named.conf, Doug.  After that: /var/mdw/scripts/named restart

    Kip, I would not use the UTM as a primary, internal DNS server except in a very, very small office.  That said, internal DNS servers could have the same exposure.

    Cheers - Bob

    NOTE: Edited substantially an hour later than the time stamp - I didn't realize that much time had passed!

     
    Sophos UTM Community Moderator
    Sophos Certified Architect - UTM
    Sophos Certified Engineer - XG
    Gold Solution Partner since 2005
    MediaSoft, Inc. USA
  • Nothing to do with config.  A dns server should answer the client question the way it is asked.   If the client says "do not recurse" then it should not recurse.  Seems like a basic issue of RFC and securtity compliance.

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