One document matched: draft-ietf-dprive-problem-statement-01.xml

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<!ENTITY rfc6347 SYSTEM
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<!ENTITY rfc6973 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.6973.xml">
<!ENTITY rfc7258 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.7258.xml">
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<rfc docName="draft-ietf-dprive-problem-statement-01" category="info" ipr="trust200902">
<?rfc toc="yes"?>
<?rfc strict="yes"?> 
<front>
<title abbrev="DNS privacy">DNS privacy considerations</title>
<author fullname="Stephane Bortzmeyer" initials="S." surname="Bortzmeyer">
<organization>AFNIC</organization>
<address><postal><street>1, rue Stephenson</street><code>78180</code><city>Montigny-le-Bretonneux</city><country>France</country></postal> <phone>+33 1 39 30 83 46</phone><email>bortzmeyer+ietf@nic.fr</email><uri>http://www.afnic.fr/</uri></address>
</author>
<date month="January" year="2015"/>
<workgroup>DNS PRIVate Exchange (dprive) Working Group</workgroup>
<abstract>
<t>This document describes the privacy issues associated with the use
of the
DNS by Internet users. It is intended to be mostly an analysis of the
present situation, in the spirit of section 8 of <xref target="RFC6973"/> and it does not
prescribe solutions.</t>
<t>Discussions of the document should take place on the
DPRIVE working group mailing list <xref target="dprive"/>.</t>
</abstract>
</front>

<middle>
<section anchor="introduction" title="Introduction">
<t>The Domain Name System is specified in <xref
target="RFC1034"/> and <xref target="RFC1035"/>. It is one of the
most important infrastructure components of the Internet and one of
the most often ignored or misunderstood. Almost every activity on the
Internet starts with a DNS query (and often several). Its use has many privacy
implications and we try to give here a comprehensive and accurate
list.</t>
<t>Let us begin with a simplified reminder of how the DNS
works. (REMOVE BEFORE PUBLICATION: We
hope that the document <xref target="I-D.hoffman-dns-terminology"/> will be
published as a RFC so most of this section could be replaced by a
reference to it.)
A client, the stub resolver, issues a DNS query
to a server, the recursive resolver (also called caching resolver or full resolver or simply resolver recursive name server). 
Let's use the query "What are the AAAA records for
www.example.com?" as an example. AAAA is the qtype (Query type), and
www.example.com is the qname (Query Name). The recursive resolver will first
query the root nameservers. In most cases, the root nameservers will
send a referral. In this example, the referral will be to .com
nameservers. The resolver repeats the query to
one of the .com nameservers. The .com nameserver, in turn, will refer to
the example.com nameservers. The example.com nameserver will then
return the answer.
The root name servers, the name servers of
.com and those of example.com are called authoritative name servers. It is important, when analyzing the privacy
issues, to remember that the question asked to all these name servers
is always the original question, not a derived question. Unlike what
many "DNS for dummies" articles say, the question sent to the root
name servers is "What are the
AAAA records for www.example.com?", not "What are the name servers
of .com?". By repeating the full question, instead of just the relevant part
of the question to the next in line, the DNS provides more information
than necessary to the nameserver.</t>
<t>Because the DNS uses caching heavily, not all questions are sent to
the authoritative name servers. If the stub resolver, a few seconds
later, asks to the recursive resolver "What are the SRV records of
_xmpp-server._tcp.example.com?", the recursive resolver will remember that it
knows the name servers of example.com and will just query them,
bypassing the root and .com. Because there is typically no caching in
the stub resolver, the recursive resolver, unlike the authoritative servers, sees everything.
</t>
<t>It should be noted that DNS recursive resolvers sometimes forward requests to
bigger machines, with a larger and more shared cache, the
forwarders (and the query hierarchy can be even deeper, with more than two levels of recursive resolvers). From the point of view of privacy, forwarders are like
resolvers, except that the caching in the recursive resolvers before them
decreases the amount of data they can see.</t>
<t>All this DNS traffic is today sent in clear (unencryted), except a
few cases when the IP traffic is protected, for instance in an IPsec VPN.</t>
<t>Today, almost all DNS queries are sent over UDP. This has
practical consequences, when considering a possible privacy technique, encryption of the
traffic: some encryption solutions are only designed for TCP, not UDP.</t>
<t>Another important point to keep in mind when analyzing the privacy
issues of DNS is the mix of many sort of DNS requests received by a
server. Let's assume the eavesdropper wants to know which Web page is
viewed by an user. For a typical Web page displayed by the user,
there are three sorts of DNS requests being issued:
<list>
<t>Primary request: this is the domain name in the URL that the user typed or
selected from a bookmark or choose by clicking on an
hyperlink. Presumably, this is what is of interest for the
eavesdropper.</t>
<t>Secondary requests: these are the additional requests performed by the user
agent (here, the Web browser) without any direct involvement or
knowledge of the user. For the Web, they are triggered by embedded
content, CSS sheets, JavaScript code, embedded images, etc. In some
cases, there can be dozens of domain names in different contexts on a single Web page.</t>
<t>Tertiary requests: these are the additional requests performed by the DNS
system itself. For instance, if the answer to a query is a referral to
a set of name servers, and the glue is not returned, the resolver will
have to do tertiary requests to turn name servers' names into IP addresses.
Similarly, even if glue records are returned, a careful recursive
server will do tertiary requests to verify the IP addresses of
those records.</t>
</list>
It can be noted also that, in the case of a typical Web browser, more
DNS requests are sent, for instance to prefetch resources that the
user may query later, or when autocompleting the URL in the address
bar (which obviously is a big privacy concern).
</t>
<t>For privacy-related terms, we will use here the terminology of <xref target="RFC6973"/>.</t>
</section>

<section title="Risks">

<t>This document focuses mostly on the study of privacy risks for the end-user (the one performing DNS
requests). We consider the risks of pervasive surveillance (<xref
target="RFC7258"/>) and also risks coming from a more focused
surveillance. Privacy risks for the holder of a zone (the risk that
someone gets the data) are discussed in <xref target="RFC5936"/>. Non-privacy
risks (such as cache poisoning) are out of scope.</t>

<section title="The alleged public nature of DNS data">

<t>It has long been claimed that "the data in the DNS is public".  While
this sentence makes sense for an Internet-wide lookup system, there
are multiple facets to the data and metadata involved that deserve a more
detailed look.  First, access control lists and private namespaces
nonwithstanding, the DNS operates under the assumption that public
facing authoritative name servers will respond to "usual" DNS queries
for any zone they are authoritative for without further
authentication or authorization of the client (resolver).  Due to the lack of search
capabilities, only a given qname will reveal the resource records
associated with that name (or that name's non-existence).  In other
words: one needs to know what to ask for, in order to receive a response.  The
zone transfer qtype <xref target="RFC5936"/> is often blocked or restricted to
authenticated/authorized access to enforce this difference (and maybe
for other, more dubious reasons).</t>
<t>Another differentiation to be considered is between the DNS data
itself and a particular transaction (i.e., a DNS name lookup). DNS
data and the results of a DNS query are public, within the boundaries
described above, and may not have any confidentiality requirements.
However, the same is not true of a single transaction or sequence of
transactions; that transaction is not/should not be public. A typical example
from outside the DNS world is: the Web site of Alcoholics Anonymous is public; the fact that you visit it should not be.</t>
</section>

<section title="Data in the DNS request">
<t>The DNS request includes many fields but two of them seem particularly
relevant for the privacy issues, the qname and the source IP
address. "source IP address" is used in a loose sense of "source IP address
+ maybe source port", because the port is also in the request and can be used to sort out several users
sharing an IP address (behind a CGN for instance).</t>
<t>The qname is the full name sent by the user. It gives
information about what the user does ("What are the MX records of
example.net?" means he probably wants to send email to someone at
example.net, which may be a domain used by only a few persons and
therefore very revealing about communication relationships). Some qnames are more sensitive than
others. For instance, querying the A record of google-analytics.com
reveals very little (everybody visits Web sites which use Google
Analytics) but querying the A record of www.verybad.example where
verybad.example is the domain of an illegal or very offensive
organization may create more problems for the user. Also, sometimes,
the qname embeds the software one uses, which could be a privacy
issue. For instance,
_ldap._tcp.Default-First-Site-Name._sites.gc._msdcs.example.org. There
are also some
BitTorrent clients that query a SRV record for _bittorrent-tracker._tcp.domain.example.</t>

<t>Another important thing about the privacy of the qname is the
future usages. Today, the lack of privacy is an obstacle to putting
potentially sensitive or personally identifiable data in the DNS. At the moment your DNS traffic might
reveal that you are doing email but not with whom. If your MUA starts
looking up PGP keys in the DNS <xref
target="I-D.wouters-dane-openpgp"/> then privacy becomes a lot more
important. And email is just an example; there would be other really
interesting uses for a more privacy-friendly DNS.</t>

<t>For the communication between the stub resolver and the recursive resolver,
the source IP address is the address of the user's machine. Therefore, all
the issues and warnings about collection of IP addresses apply
here. For the communication between the recursive resolver and the authoritative
name servers, the source IP address has a different meaning; it does not have the same status as the source
address in a HTTP connection. It is now the IP address of the recursive resolver
which, in a way "hides" the real user. However, hiding does not always
work. Sometimes <xref
target="I-D.vandergaast-edns-client-subnet"/> is used (see its privacy analysis in <xref target="denis-edns-client-subnet"/>). Sometimes the end user has a personal recursive resolver on her
machine. In both cases, the IP address is as sensitive as it is for
HTTP.</t>
<t>A note about IP addresses: there is currently no IETF document
which describes in detail the privacy issues of IP addressing. In the
meantime, the discussion here is intended to include both IPv4 and IPv6 source
addresses. For a number of reasons their assignment and utilization characteristics
are different, which may have implications for details of information leakage
associated with the collection of source addresses. (For example, a specific IPv6
source address seen on the public Internet is less likely than an IPv4 address to
originate behind a CGN or other NAT.) However, for both IPv4 and IPv6 addresses,
it's important to note that source addresses are propagated with queries and
comprise metadata about the host, user, or application that originated them.</t>
</section>

<section title="Cache snooping">
<t>The content of recursive resolvers' caches can reveal data about
the clients using it (the privacy risks depend on the number of clients).
This information can sometimes be examined by sending DNS queries
with RD=0 to inspect cache content, particularly looking at the DNS
TTLs.  Since this also is a reconnaissance technique for subsequent
cache poisoning attacks, some counter measures have already been
developed and deployed.</t>
</section>

<section anchor="risks-on-wire" title="On the wire">
<t>DNS traffic can be seen by an eavesdropper like any other
traffic. It is typically not encrypted. (DNSSEC, specified in <xref
target="RFC4033"/> explicitly excludes confidentiality from its
goals.) So, if an initiator starts a HTTPS communication with a
recipient, while the HTTP traffic will be encrypted, the DNS exchange
prior to it will not be. When other protocols will become more and
more privacy-aware and secured against surveillance, the DNS risks to
become "the weakest link" in privacy.</t>
<t>An important specificity of the DNS traffic is that it may take a
different path than the communication between the initiator and the
recipient. For instance, an eavesdropper may be unable to tap the wire
between the initiator and the recipient but may have access to the
wire going to the recursive resolver, or to the authoritative name servers.</t>
<t>The best place to tap, from an eavesdropper's point of view, is clearly
between the stub resolvers and the recursive resolvers, because traffic is not
limited by DNS caching.</t>
<t>The attack surface between the stub resolver and the rest of the world
can vary widely depending upon how the end user's computer is
configured. By order of increasing attack surface:</t>
<t>The recursive resolver can be on the end user's computer. In (currently) a small number of cases,
individuals may choose to operate their own DNS resolver on their local
machine. In this case the attack surface for the connection between
the stub resolver and the caching
resolver is limited to that single machine.
</t>
<t>The recursive resolver may be at the local network edge. For many/most enterprise networks
and for some residential users the caching resolver may exist on a server
at the edge of the local network.  In this case the attack surface is the
local network.  Note that in large enterprise networks the DNS resolver
may not be located at the edge of the local network but rather at the edge
of the overall enterprise network. In this case the enterprise network
could be thought of as similar to the IAP network referenced below.</t>
<t>The recursive resolver can be in the IAP (Internet Access Provider) premises.
For most residential users and potentially other
networks the typical case is for the end user's computer to be configured
(typically automatically through DHCP) with the addresses of the DNS
recursive resolvers at the IAP.  The attack surface for on-the-wire attacks is
therefore from the end user system across the local network and across the
IAP
network to the IAP's recursive resolvers.</t>
<t>The recursive resolver can be a public DNS service. Some machines may be configured to
use public DNS resolvers such as those operated by Google Public DNS or
OpenDNS. The end user may have configured their machine to use
these DNS recursive resolvers themselves - or their IAP may have chosen to use the public
DNS resolvers rather than operating their own resolvers.  In this case the
attack surface is the entire public Internet between the end user's
connection and the public DNS service.</t>
</section>

<section title="In the servers">
<t>Using the terminology of <xref target="RFC6973"/>, the DNS servers
(recursive resolvers and authoritative servers) are enablers: they facilitate communication between
an initiator and a recipient without being directly in the
communications path. As a result, they are often forgotten in risk
analysis. But, to quote again <xref target="RFC6973"/>, "Although [...] enablers may not generally
be considered as attackers, they may all pose privacy threats
(depending on the context) because they are able to observe, collect,
process, and transfer privacy-relevant data." In <xref
target="RFC6973"/> parlance, enablers become observers when they start
collecting data.</t>
<t>Many programs exist to collect and analyze DNS data at the servers. From the
"query log" of some programs like BIND, to tcpdump and more
sophisticated programs like <xref target="packetq">PacketQ</xref>
and <xref target="dnsmezzo">DNSmezzo</xref>. The organization
managing the DNS server can use these data itself or it can be
part of a surveillance program like <xref target="prism">PRISM</xref> and
pass data to an outside observer.</t>
<t>Sometimes, these data are kept for a long time and/or 
distributed to third parties, for research purposes <xref target="ditl"/>, for
security analysis, or for surveillance tasks. Also, there are
observation points in the network which gather DNS data and then make
it accessible to third-parties for research or security purposes
("<xref target="passive-dns">passive DNS</xref>").</t>

<section title="In the recursive resolvers">
<t>Recursive Resolvers see all the traffic since there is typically no
caching before them. To summarize: your recursive resolver knows a lot about you. The resolver
of a large IAP, or a large public resolver can collect data from many
users. You may get an idea of the data collected by reading <eref
target="https://developers.google.com/speed/public-dns/privacy">the
privacy policy of a big public resolver</eref>. <!-- TODO published
policies of OpenDNS: nothing found on their Web site, only for the
Web, not for the DNS service, question sent, indirect reply received
TODO summarize --></t>
</section>

<section title="In the authoritative name servers">
<t>Unlike what happens for recursive resolvers, observation capabilities of authoritative name servers are limited by
caching; they see only the requests for which the answer was not in the cache. For aggregated
statistics ("What is the percentage of LOC queries?"), this is
sufficient; but it prevents an observer from seeing everything.
Still, the authoritative name servers see a part of the traffic, and
this subset may be sufficient to violate some privacy expectations.</t>
<t>Also, the end user has typically some legal/contractual link with
the recursive resolver (he has chosen the IAP, or he has chosen to use a given public
resolver), while having no control and perhaps no awareness of the role of the
authoritative name servers and their observation abilities.</t>
<!-- Some people said it is too speculative, may be even too political. -->
<t>It is an interesting question whether the privacy issues are bigger
in the root or in a large TLD. The root sees the traffic for all the TLDs (and the huge
amount of traffic for non-existing TLDs), but a large TLDs has less caching
before it.</t>
<t>As noted before, using a local resolver or a resolver close to the
machine decreases the attack surface for an on-the-wire
eavesdropper. But it may decrease privacy against an observer located
on an authoritative name server. This authoritative name server
will see the IP address of the end client, instead of the address of a
big recursive resolver shared by many users.</t>
<t>This "protection", when using a large resolver with many clients, is no longer present if <xref
target="I-D.vandergaast-edns-client-subnet"/> is used because, in this
case, the authoritative name server sees the original IP address (or prefix, depending on the setup).</t>
<t>As of today, all the instances of one root name server, L-root,
receive together around 20,000 queries per second<!-- http://dns.icann.org/cgi-bin/dsc-grapher.pl?plot=bynode&server=L-root Same thing for K http://k.root-servers.org/ -->. While most of it is junk (errors on
the TLD name), it gives an idea of the amount of big data which pours
into name servers.</t>
<t>Many domains, including TLDs, are partially hosted by third-party
servers, sometimes in a different country. The contracts between the
domain manager and these servers may or may not take privacy into
account. Whatever the contract, the third-party hoster may be honest or not but, in any case,
it will have to follow its local laws. It may be surprising for an end-user that requests to a
given ccTLD may go to servers managed by organisations outside of the country.</t>
<t>Also, it seems (TODO: actual numbers requested) that there is a
strong concentration of authoritative name servers among "popular"
domains (such as the Alexa Top N list). With the control (or the ability
to sniff the traffic) of a few name servers, you can gather a lot of
information.</t>
</section>

<section title="Rogue servers">
<t>A rogue DHCP server,
or a trusted DHCP server that has had its configuration altered by malicious parties,
can direct you to a rogue recursive resolver. Most of the
times, it seems to be done to divert traffic, by providing lies for
some domain names. But it could be used just to
capture the traffic and gather information about you. Same thing for
malware like DNSchanger<xref target="dnschanger"/> which changes the
recursive resolver in the machine's configuration, or with transparent DNS proxies in the network that
will divert the traffic intended for a legitimate DNS server (for instance <xref target="turkey-googledns"/>).</t>
</section>

</section>

</section>

<section title="Actual "attacks"">
<t>A very quick examination of DNS traffic may lead to the false
conclusion that extracting the needle from the haystack is
difficult. "Interesting" primary DNS requests are mixed with useless
(for the eavesdropper) second and
tertiary requests (see the terminology in <xref
target="introduction"/>). But, in this time of "big data" processing,
powerful techniques now exist to get from the raw data to what you're
actually interested in.</t>
<t>Many research papers about malware detection use DNS traffic to
detect "abnormal" behaviour that can be traced back to the activity of
malware on infected machines. Yes, this research was done for the good but,
technically, it is a privacy attack and it demonstrates the power of
the observation of DNS traffic. See <xref target="dns-footprint"/>,
<xref target="dagon-malware"/> and <xref
target="darkreading-dns"/>.</t>
<t><xref target="passive-dns">Passive DNS systems</xref> allow reconstruction of the data of sometimes
an entire zone. It is used for many reasons, some good, some bad. It
is an example of a privacy issue even when no source IP address is kept.</t>
</section>

<section title="Legalities">
<t>To our knowledge, there are no specific privacy laws for DNS
data. Interpreting general privacy laws like
[data-protection-directive] (European Union) in the context of DNS traffic data is not
an easy task and it seems there is no court precedent here.</t>
</section>

<section title="Security considerations">
<t>This document is entirely about security, more precisely
privacy. It just lays down the problem, it does not try to set
requirments (with the choices and compromises they imply), much less
to define solutions. A document on requirments for DNS privacy is
<xref target="I-D.hallambaker-dnse"/>.  Possible solutions to the
issues described here are discussed in other documents (currently too
many to be listed here).</t>

</section>

<section title="Acknowledgments">
<t>Thanks to Nathalie Boulvard and to the CENTR members for the
original work which leaded to this document. Thanks to Ondrej Sury for the
interesting discussions. Thanks to Mohsen Souissi and John Heidemann for
proofreading, to Paul Hoffman, Marcos Sanz and Warren Kumari for
proofreading, technical remarks, and many readability improvements. Thanks to Dan York, Suzanne Woolf, Tony Finch, Peter Koch and Frank Denis for good written contributions.</t>
</section>

</middle>

<back>

<references title='Normative References'>
&rfc1034;
&rfc1035;
&rfc2119;
&rfc6973;
&rfc7258;
</references>

<references title='Informative References'>
<!-- TODO Please alphabetize, at least the drafts -->
&rfc4033;
&rfc5936;
&I-D.vandergaast-edns-client-subnet;
&I-D.hallambaker-dnse;
&I-D.wouters-dane-openpgp;
&I-D.hoffman-dns-terminology; <!-- TODO: To be moved to Normative if
published and used for reference -->

<reference anchor="dprive" target="http://www.ietf.org/mail-archive/web/dns-privacy/">
<front>
<title>The DPRIVE working group</title>
<author fullname="IETF" surname="IETF" initials="DPRIVE"/>
<date month="March" year="2014"/>
<abstract>
<t>This IETF Working Group is for the discussion of the problem statement 
surrounding the addition of privacy to the DNS protocol, and for the possible solutions.</t>
</abstract>
</front>
</reference>

<reference anchor="denis-edns-client-subnet" target="https://00f.net/2013/08/07/edns-client-subnet/">
<front>
<title>Security and privacy issues of edns-client-subnet</title>
<author fullname="Frank Denis" surname="Denis" initials="F"/>
<date month="August" year="2013"/>
</front>
</reference>

<reference anchor="dagon-malware" target="https://www.dns-oarc.net/files/workshop-2007/Dagon-Resolution-corruption.pdf">
<front>
<title>Corrupted DNS Resolution Paths: The Rise of a Malicious
Resolution Authority</title>
<author surname="Dagon" initials="D." fullname="David Dagon"/>
<date year="2007"/>
<abstract>
<t>Presented at the DNS-OARC meeting in Atlanta.</t>
</abstract>
</front>
</reference>

<reference anchor="dns-footprint" target="https://www.dns-oarc.net/files/workshop-201010/OARC-ers-20101012.pdf">
<front>
<title>DNS footprint of malware</title>
<author fullname="Ed Stoner" surname="Stoner" initials="E."/>
<date day="13" month="October" year="2010"/>
<abstract>
<t>Finding Malicious Activity Using Network Flow Data. Presented at the DNS-OARC meeting in Denver.</t>
</abstract>
</front>
</reference>

<reference anchor="darkreading-dns" target="http://www.darkreading.com/monitoring/got-malware-three-signs-revealed-in-dns/240154181">
<front>
<title>Got Malware? Three Signs Revealed In DNS Traffic</title>
<author fullname="Robert Lemos" surname="Lemos" initials="R."/>
<date month="May" year="2013" day="3"/>
<abstract>
<t>Monitoring your network's requests for domain lookups can reveal
network problems and potential malware infections.</t>
</abstract>
</front>
</reference>

<reference anchor="dnschanger" target="http://en.wikipedia.org/wiki/DNSChanger">
<front>
<title>DNSchanger</title>
<author fullname="Wikipedia" surname="Wikipedia"/>
<date month="November" year="2011"/>
</front>
</reference>

<reference anchor="packetq" target="https://github.com/dotse/packetq/wiki">
<front>
<title>PacketQ, a simple tool to make SQL-queries against PCAP-files</title>
<author fullname="Dot SE" surname="Dot SE"/>
<date year="2011"/>
<abstract><t>A tool that provides a basic SQL-frontend to
PCAP-files. Outputs JSON, CSV and XML and includes a build-in
webserver with JSON-api and a nice looking AJAX GUI.</t></abstract>
</front>
</reference>

<reference anchor="dnsmezzo" target="http://www.dnsmezzo.net/">
<front>
<title>DNSmezzo</title>
<author fullname="Stéphane Bortzmeyer" surname="Bortzmeyer" initials="S."/>
<date year="2009"/>
<abstract><t>DNSmezzo is a framework for the capture and analysis of DNS packets. It allows the manager of a DNS name server to get information such as the top N domains requests, the percentage of IPv6 queries, the most talkative clients, etc. It is part of the broader program DNSwitness.</t></abstract>
</front>
</reference>

<reference anchor="prism" target="http://en.wikipedia.org/wiki/PRISM_%28surveillance_program%29">
<front>
<title>PRISM</title>
<author fullname="National Security Agency" surname="NSA"/>
<date year="2007"/>
</front>
</reference>

<reference anchor="ditl" target="http://www.caida.org/projects/ditl/">
<front>
<title>A Day in the Life of the Internet (DITL)</title>
<author fullname="CAIDA" surname="CAIDA"/>
<date year="2002"/>
<abstract>
<t>CAIDA, ISC, DNS-OARC, and many partnering root nameserver operators
and other organizations to coordinate and conduct large-scale,
simultaneous traffic data collection events with the goal of capturing
datasets of strategic interest to researchers. Over the last several
years, we have come to refer to this project and related activities as
"A Day in the Life of the Internet" (DITL).</t>
</abstract>
</front>
</reference>

<reference anchor="turkey-googledns" target="http://www.bortzmeyer.org/dns-routing-hijack-turkey.html">
<front>
<title>Hijacking of public DNS servers in Turkey, through routing</title>
<author fullname="Stephane Bortzmeyer" initials="S." surname="Bortzmeyer"/>
<date year="2014"/>
<abstract>
<t>Internet access providers in Turkey started, not only to install lying DNS resolvers, but also to hijack the IP addresses of some popular open DNS resolvers, like Google Public DNS.</t>
</abstract>
</front>
</reference>

<reference anchor="data-protection-directive" target="http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31995L0046:EN:HTML">
<front>
<title>European directive 95/46/EC on the protection of individuals
with regard to the processing of personal data and on the free
movement of such data</title>
<author fullname="European Parliament" surname="Europe"/>
<date day="23" month="November" year="1995"/>
</front>
</reference>

<reference anchor="passive-dns" target="http://www.enyo.de/fw/software/dnslogger/#2">
<front>
<title>Passive DNS Replication</title>
<author fullname="Florian Weimer" initials="F." surname="Weimer"/>
<date month="April"  year="2005"/>
<abstract>
<t>FIRST 17</t>
</abstract>
</front>
</reference>

<reference anchor="tor-leak" target="https://trac.torproject.org/projects/tor/wiki/doc/TorFAQ#IkeepseeingthesewarningsaboutSOCKSandDNSandinformationleaks.ShouldIworry">
<front>
<title>DNS leaks in Tor</title>
<author fullname="Tor Project" surname="Tor"/>
<date year="2013"/>
</front>
</reference>

<reference anchor="yanbin-tsudik" target="http://arxiv.org/abs/0910.2472">
<front>
<title>Towards Plugging Privacy Leaks in the Domain Name System</title>
<author fullname="Yanbin Lu" surname="Yanbin" initials="L."/>
<author fullname="Gene Tsudik" surname="Tsudik" initials="G."/>
<date year="2009"/>
<abstract>
<t>Peer-to-peer computing (p2p), 2010 IEEE tenth
international conference on, IEEE, Piscataway, NJ, USA, 25 August 2010
(2010-08-25), pages 1-10, XP031752227, ISBN: 978-1-4244-7140-9</t>
<t>Actually, it is not about the DNS but about a complete replacement, using DHTs for resolution.</t>
</abstract></front>
</reference>

<reference anchor="castillo-garcia" target="http://deic.uab.es/~joaquin/papers/is08.pdf">
<front>
<title>Anonymous Resolution of DNS Queries</title>
<author initials="S." surname="Castillo-Perez" fullname="S. Castillo-Perez"/>
<author initials="J." surname="Garcia-Alfaro" fullname="J.Garcia-Alfaro"/>
<date year="2008"/>
<abstract>
<t>OTM 2008 Confederated International Conferences, CoopIS, DOA, GADA, IS, and ODBASE 2008, Monterrey, Mexico, November 9-14, 2008, Proceedings</t>
<t>Focus on ENUM privacy risks. A suggested solution is to add gratuitous queries, in order to hide the real ones.</t>
</abstract>
</front>
</reference>

<reference anchor="fangming-hori-sakurai" target="http://dl.acm.org/citation.cfm?id=1262690.1262986">
<front>
<title>Analysis of Privacy Disclosure in DNS Query</title>
<author fullname="Fangming Zhao" surname="Fangming"/>
<author fullname="Yoshiaki Hori" surname="Hori" initials="Y."/>
<author fullname="Kouichi Sakurai" surname="Sakurai" initials="K."/>
<date year="2007"/>
<abstract>
<t>DOI: 10.1109/MUE.2007.84 Conference: 2007 International Conference on Multimedia and Ubiquitous Engineering (MUE 2007), 26-28 April 2007, Seoul, Korea</t>
<t>Not available online.</t>
</abstract>
</front>
</reference>

<reference anchor="federrath-fuchs-herrmann-piosecny" target="https://svs.informatik.uni-hamburg.de/publications/2011/2011-09-14_FFHP_PrivacyPreservingDNS_ESORICS2011.pdf">
<front>
<title>Privacy-Preserving DNS: Analysis of Broadcast, Range Queries and Mix-Based Protection Methods</title>
<author fullname="Hannes Federrath" surname="Federrath" initials="H."/>
<author fullname="Karl-Peter Fuchs" surname="Fuchs" initials="K.-P."/>
<author fullname="Dominik Herrmann" surname="Herrmann" initials="D."/>
<author fullname="Christopher Piosecny" surname="Piosecny" initials="C."/>
<date year="2011"/>
<abstract>
<t>COMPUTER SECURITY ESORICS 2011, SPRINGER BERLIN HEIDELBERG, BERLIN, HEIDELBERG, PAGE(S) 665 - 683, XP019164096, ISBN: 978-3-642-23821-5</t>
<t>Privacy is improved by broadcasting of the most common names plus mixes (a Tor-like routing system).</t>
</abstract>
</front>
</reference>

</references>

</back>

</rfc>