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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 DNS PRIVate Exchange (dprive) Working Group S. Bortzmeyer 3 Internet-Draft AFNIC 4 Intended status: Informational January 7, 2015 5 Expires: July 11, 2015 7 DNS privacy considerations 8 draft-ietf-dprive-problem-statement-01 10 Abstract 12 This document describes the privacy issues associated with the use of 13 the DNS by Internet users. It is intended to be mostly an analysis 14 of the present situation, in the spirit of section 8 of [RFC6973] and 15 it does not prescribe solutions. 17 Discussions of the document should take place on the DPRIVE working 18 group mailing list [dprive]. 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at http://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on July 11, 2015. 37 Copyright Notice 39 Copyright (c) 2015 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (http://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 55 2. Risks . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 56 2.1. The alleged public nature of DNS data . . . . . . . . . . 4 57 2.2. Data in the DNS request . . . . . . . . . . . . . . . . . 5 58 2.3. Cache snooping . . . . . . . . . . . . . . . . . . . . . 6 59 2.4. On the wire . . . . . . . . . . . . . . . . . . . . . . . 6 60 2.5. In the servers . . . . . . . . . . . . . . . . . . . . . 7 61 2.5.1. In the recursive resolvers . . . . . . . . . . . . . 8 62 2.5.2. In the authoritative name servers . . . . . . . . . . 8 63 2.5.3. Rogue servers . . . . . . . . . . . . . . . . . . . . 9 64 3. Actual "attacks" . . . . . . . . . . . . . . . . . . . . . . 10 65 4. Legalities . . . . . . . . . . . . . . . . . . . . . . . . . 10 66 5. Security considerations . . . . . . . . . . . . . . . . . . . 10 67 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10 68 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 69 7.1. Normative References . . . . . . . . . . . . . . . . . . 11 70 7.2. Informative References . . . . . . . . . . . . . . . . . 11 71 7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 14 72 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 14 74 1. Introduction 76 The Domain Name System is specified in [RFC1034] and [RFC1035]. It 77 is one of the most important infrastructure components of the 78 Internet and one of the most often ignored or misunderstood. Almost 79 every activity on the Internet starts with a DNS query (and often 80 several). Its use has many privacy implications and we try to give 81 here a comprehensive and accurate list. 83 Let us begin with a simplified reminder of how the DNS works. 84 (REMOVE BEFORE PUBLICATION: We hope that the document 85 [I-D.hoffman-dns-terminology] will be published as a RFC so most of 86 this section could be replaced by a reference to it.) A client, the 87 stub resolver, issues a DNS query to a server, the recursive resolver 88 (also called caching resolver or full resolver or simply resolver 89 recursive name server). Let's use the query "What are the AAAA 90 records for www.example.com?" as an example. AAAA is the qtype 91 (Query type), and www.example.com is the qname (Query Name). The 92 recursive resolver will first query the root nameservers. In most 93 cases, the root nameservers will send a referral. In this example, 94 the referral will be to .com nameservers. The resolver repeats the 95 query to one of the .com nameservers. The .com nameserver, in turn, 96 will refer to the example.com nameservers. The example.com 97 nameserver will then return the answer. The root name servers, the 98 name servers of .com and those of example.com are called 99 authoritative name servers. It is important, when analyzing the 100 privacy issues, to remember that the question asked to all these name 101 servers is always the original question, not a derived question. 102 Unlike what many "DNS for dummies" articles say, the question sent to 103 the root name servers is "What are the AAAA records for 104 www.example.com?", not "What are the name servers of .com?". By 105 repeating the full question, instead of just the relevant part of the 106 question to the next in line, the DNS provides more information than 107 necessary to the nameserver. 109 Because the DNS uses caching heavily, not all questions are sent to 110 the authoritative name servers. If the stub resolver, a few seconds 111 later, asks to the recursive resolver "What are the SRV records of 112 _xmpp-server._tcp.example.com?", the recursive resolver will remember 113 that it knows the name servers of example.com and will just query 114 them, bypassing the root and .com. Because there is typically no 115 caching in the stub resolver, the recursive resolver, unlike the 116 authoritative servers, sees everything. 118 It should be noted that DNS recursive resolvers sometimes forward 119 requests to bigger machines, with a larger and more shared cache, the 120 forwarders (and the query hierarchy can be even deeper, with more 121 than two levels of recursive resolvers). From the point of view of 122 privacy, forwarders are like resolvers, except that the caching in 123 the recursive resolvers before them decreases the amount of data they 124 can see. 126 All this DNS traffic is today sent in clear (unencryted), except a 127 few cases when the IP traffic is protected, for instance in an IPsec 128 VPN. 130 Today, almost all DNS queries are sent over UDP. This has practical 131 consequences, when considering a possible privacy technique, 132 encryption of the traffic: some encryption solutions are only 133 designed for TCP, not UDP. 135 Another important point to keep in mind when analyzing the privacy 136 issues of DNS is the mix of many sort of DNS requests received by a 137 server. Let's assume the eavesdropper wants to know which Web page 138 is viewed by an user. For a typical Web page displayed by the user, 139 there are three sorts of DNS requests being issued: 141 Primary request: this is the domain name in the URL that the user 142 typed or selected from a bookmark or choose by clicking on an 143 hyperlink. Presumably, this is what is of interest for the 144 eavesdropper. 146 Secondary requests: these are the additional requests performed by 147 the user agent (here, the Web browser) without any direct 148 involvement or knowledge of the user. For the Web, they are 149 triggered by embedded content, CSS sheets, JavaScript code, 150 embedded images, etc. In some cases, there can be dozens of 151 domain names in different contexts on a single Web page. 153 Tertiary requests: these are the additional requests performed by 154 the DNS system itself. For instance, if the answer to a query is 155 a referral to a set of name servers, and the glue is not returned, 156 the resolver will have to do tertiary requests to turn name 157 servers' names into IP addresses. Similarly, even if glue records 158 are returned, a careful recursive server will do tertiary requests 159 to verify the IP addresses of those records. 161 It can be noted also that, in the case of a typical Web browser, more 162 DNS requests are sent, for instance to prefetch resources that the 163 user may query later, or when autocompleting the URL in the address 164 bar (which obviously is a big privacy concern). 166 For privacy-related terms, we will use here the terminology of 167 [RFC6973]. 169 2. Risks 171 This document focuses mostly on the study of privacy risks for the 172 end-user (the one performing DNS requests). We consider the risks of 173 pervasive surveillance ([RFC7258]) and also risks coming from a more 174 focused surveillance. Privacy risks for the holder of a zone (the 175 risk that someone gets the data) are discussed in [RFC5936]. Non- 176 privacy risks (such as cache poisoning) are out of scope. 178 2.1. The alleged public nature of DNS data 180 It has long been claimed that "the data in the DNS is public". While 181 this sentence makes sense for an Internet-wide lookup system, there 182 are multiple facets to the data and metadata involved that deserve a 183 more detailed look. First, access control lists and private 184 namespaces nonwithstanding, the DNS operates under the assumption 185 that public facing authoritative name servers will respond to "usual" 186 DNS queries for any zone they are authoritative for without further 187 authentication or authorization of the client (resolver). Due to the 188 lack of search capabilities, only a given qname will reveal the 189 resource records associated with that name (or that name's non- 190 existence). In other words: one needs to know what to ask for, in 191 order to receive a response. The zone transfer qtype [RFC5936] is 192 often blocked or restricted to authenticated/authorized access to 193 enforce this difference (and maybe for other, more dubious reasons). 195 Another differentiation to be considered is between the DNS data 196 itself and a particular transaction (i.e., a DNS name lookup). DNS 197 data and the results of a DNS query are public, within the boundaries 198 described above, and may not have any confidentiality requirements. 199 However, the same is not true of a single transaction or sequence of 200 transactions; that transaction is not/should not be public. A 201 typical example from outside the DNS world is: the Web site of 202 Alcoholics Anonymous is public; the fact that you visit it should not 203 be. 205 2.2. Data in the DNS request 207 The DNS request includes many fields but two of them seem 208 particularly relevant for the privacy issues, the qname and the 209 source IP address. "source IP address" is used in a loose sense of 210 "source IP address + maybe source port", because the port is also in 211 the request and can be used to sort out several users sharing an IP 212 address (behind a CGN for instance). 214 The qname is the full name sent by the user. It gives information 215 about what the user does ("What are the MX records of example.net?" 216 means he probably wants to send email to someone at example.net, 217 which may be a domain used by only a few persons and therefore very 218 revealing about communication relationships). Some qnames are more 219 sensitive than others. For instance, querying the A record of 220 google-analytics.com reveals very little (everybody visits Web sites 221 which use Google Analytics) but querying the A record of 222 www.verybad.example where verybad.example is the domain of an illegal 223 or very offensive organization may create more problems for the user. 224 Also, sometimes, the qname embeds the software one uses, which could 225 be a privacy issue. For instance, _ldap._tcp.Default-First-Site- 226 Name._sites.gc._msdcs.example.org. There are also some BitTorrent 227 clients that query a SRV record for _bittorrent- 228 tracker._tcp.domain.example. 230 Another important thing about the privacy of the qname is the future 231 usages. Today, the lack of privacy is an obstacle to putting 232 potentially sensitive or personally identifiable data in the DNS. At 233 the moment your DNS traffic might reveal that you are doing email but 234 not with whom. If your MUA starts looking up PGP keys in the DNS 235 [I-D.wouters-dane-openpgp] then privacy becomes a lot more important. 236 And email is just an example; there would be other really interesting 237 uses for a more privacy-friendly DNS. 239 For the communication between the stub resolver and the recursive 240 resolver, the source IP address is the address of the user's machine. 241 Therefore, all the issues and warnings about collection of IP 242 addresses apply here. For the communication between the recursive 243 resolver and the authoritative name servers, the source IP address 244 has a different meaning; it does not have the same status as the 245 source address in a HTTP connection. It is now the IP address of the 246 recursive resolver which, in a way "hides" the real user. However, 247 hiding does not always work. Sometimes 248 [I-D.vandergaast-edns-client-subnet] is used (see its privacy 249 analysis in [denis-edns-client-subnet]). Sometimes the end user has 250 a personal recursive resolver on her machine. In both cases, the IP 251 address is as sensitive as it is for HTTP. 253 A note about IP addresses: there is currently no IETF document which 254 describes in detail the privacy issues of IP addressing. In the 255 meantime, the discussion here is intended to include both IPv4 and 256 IPv6 source addresses. For a number of reasons their assignment and 257 utilization characteristics are different, which may have 258 implications for details of information leakage associated with the 259 collection of source addresses. (For example, a specific IPv6 source 260 address seen on the public Internet is less likely than an IPv4 261 address to originate behind a CGN or other NAT.) However, for both 262 IPv4 and IPv6 addresses, it's important to note that source addresses 263 are propagated with queries and comprise metadata about the host, 264 user, or application that originated them. 266 2.3. Cache snooping 268 The content of recursive resolvers' caches can reveal data about the 269 clients using it (the privacy risks depend on the number of clients). 270 This information can sometimes be examined by sending DNS queries 271 with RD=0 to inspect cache content, particularly looking at the DNS 272 TTLs. Since this also is a reconnaissance technique for subsequent 273 cache poisoning attacks, some counter measures have already been 274 developed and deployed. 276 2.4. On the wire 278 DNS traffic can be seen by an eavesdropper like any other traffic. 279 It is typically not encrypted. (DNSSEC, specified in [RFC4033] 280 explicitly excludes confidentiality from its goals.) So, if an 281 initiator starts a HTTPS communication with a recipient, while the 282 HTTP traffic will be encrypted, the DNS exchange prior to it will not 283 be. When other protocols will become more and more privacy-aware and 284 secured against surveillance, the DNS risks to become "the weakest 285 link" in privacy. 287 An important specificity of the DNS traffic is that it may take a 288 different path than the communication between the initiator and the 289 recipient. For instance, an eavesdropper may be unable to tap the 290 wire between the initiator and the recipient but may have access to 291 the wire going to the recursive resolver, or to the authoritative 292 name servers. 294 The best place to tap, from an eavesdropper's point of view, is 295 clearly between the stub resolvers and the recursive resolvers, 296 because traffic is not limited by DNS caching. 298 The attack surface between the stub resolver and the rest of the 299 world can vary widely depending upon how the end user's computer is 300 configured. By order of increasing attack surface: 302 The recursive resolver can be on the end user's computer. In 303 (currently) a small number of cases, individuals may choose to 304 operate their own DNS resolver on their local machine. In this case 305 the attack surface for the connection between the stub resolver and 306 the caching resolver is limited to that single machine. 308 The recursive resolver may be at the local network edge. For many/ 309 most enterprise networks and for some residential users the caching 310 resolver may exist on a server at the edge of the local network. In 311 this case the attack surface is the local network. Note that in 312 large enterprise networks the DNS resolver may not be located at the 313 edge of the local network but rather at the edge of the overall 314 enterprise network. In this case the enterprise network could be 315 thought of as similar to the IAP network referenced below. 317 The recursive resolver can be in the IAP (Internet Access Provider) 318 premises. For most residential users and potentially other networks 319 the typical case is for the end user's computer to be configured 320 (typically automatically through DHCP) with the addresses of the DNS 321 recursive resolvers at the IAP. The attack surface for on-the-wire 322 attacks is therefore from the end user system across the local 323 network and across the IAP network to the IAP's recursive resolvers. 325 The recursive resolver can be a public DNS service. Some machines 326 may be configured to use public DNS resolvers such as those operated 327 by Google Public DNS or OpenDNS. The end user may have configured 328 their machine to use these DNS recursive resolvers themselves - or 329 their IAP may have chosen to use the public DNS resolvers rather than 330 operating their own resolvers. In this case the attack surface is 331 the entire public Internet between the end user's connection and the 332 public DNS service. 334 2.5. In the servers 336 Using the terminology of [RFC6973], the DNS servers (recursive 337 resolvers and authoritative servers) are enablers: they facilitate 338 communication between an initiator and a recipient without being 339 directly in the communications path. As a result, they are often 340 forgotten in risk analysis. But, to quote again [RFC6973], "Although 341 [...] enablers may not generally be considered as attackers, they may 342 all pose privacy threats (depending on the context) because they are 343 able to observe, collect, process, and transfer privacy-relevant 344 data." In [RFC6973] parlance, enablers become observers when they 345 start collecting data. 347 Many programs exist to collect and analyze DNS data at the servers. 348 From the "query log" of some programs like BIND, to tcpdump and more 349 sophisticated programs like PacketQ [packetq] and DNSmezzo 350 [dnsmezzo]. The organization managing the DNS server can use these 351 data itself or it can be part of a surveillance program like PRISM 352 [prism] and pass data to an outside observer. 354 Sometimes, these data are kept for a long time and/or distributed to 355 third parties, for research purposes [ditl], for security analysis, 356 or for surveillance tasks. Also, there are observation points in the 357 network which gather DNS data and then make it accessible to third- 358 parties for research or security purposes ("passive DNS 359 [passive-dns]"). 361 2.5.1. In the recursive resolvers 363 Recursive Resolvers see all the traffic since there is typically no 364 caching before them. To summarize: your recursive resolver knows a 365 lot about you. The resolver of a large IAP, or a large public 366 resolver can collect data from many users. You may get an idea of 367 the data collected by reading the privacy policy of a big public 368 resolver [1]. 370 2.5.2. In the authoritative name servers 372 Unlike what happens for recursive resolvers, observation capabilities 373 of authoritative name servers are limited by caching; they see only 374 the requests for which the answer was not in the cache. For 375 aggregated statistics ("What is the percentage of LOC queries?"), 376 this is sufficient; but it prevents an observer from seeing 377 everything. Still, the authoritative name servers see a part of the 378 traffic, and this subset may be sufficient to violate some privacy 379 expectations. 381 Also, the end user has typically some legal/contractual link with the 382 recursive resolver (he has chosen the IAP, or he has chosen to use a 383 given public resolver), while having no control and perhaps no 384 awareness of the role of the authoritative name servers and their 385 observation abilities. 387 It is an interesting question whether the privacy issues are bigger 388 in the root or in a large TLD. The root sees the traffic for all the 389 TLDs (and the huge amount of traffic for non-existing TLDs), but a 390 large TLDs has less caching before it. 392 As noted before, using a local resolver or a resolver close to the 393 machine decreases the attack surface for an on-the-wire eavesdropper. 394 But it may decrease privacy against an observer located on an 395 authoritative name server. This authoritative name server will see 396 the IP address of the end client, instead of the address of a big 397 recursive resolver shared by many users. 399 This "protection", when using a large resolver with many clients, is 400 no longer present if [I-D.vandergaast-edns-client-subnet] is used 401 because, in this case, the authoritative name server sees the 402 original IP address (or prefix, depending on the setup). 404 As of today, all the instances of one root name server, L-root, 405 receive together around 20,000 queries per second. While most of it 406 is junk (errors on the TLD name), it gives an idea of the amount of 407 big data which pours into name servers. 409 Many domains, including TLDs, are partially hosted by third-party 410 servers, sometimes in a different country. The contracts between the 411 domain manager and these servers may or may not take privacy into 412 account. Whatever the contract, the third-party hoster may be honest 413 or not but, in any case, it will have to follow its local laws. It 414 may be surprising for an end-user that requests to a given ccTLD may 415 go to servers managed by organisations outside of the country. 417 Also, it seems (TODO: actual numbers requested) that there is a 418 strong concentration of authoritative name servers among "popular" 419 domains (such as the Alexa Top N list). With the control (or the 420 ability to sniff the traffic) of a few name servers, you can gather a 421 lot of information. 423 2.5.3. Rogue servers 425 A rogue DHCP server, or a trusted DHCP server that has had its 426 configuration altered by malicious parties, can direct you to a rogue 427 recursive resolver. Most of the times, it seems to be done to divert 428 traffic, by providing lies for some domain names. But it could be 429 used just to capture the traffic and gather information about you. 430 Same thing for malware like DNSchanger[dnschanger] which changes the 431 recursive resolver in the machine's configuration, or with 432 transparent DNS proxies in the network that will divert the traffic 433 intended for a legitimate DNS server (for instance 434 [turkey-googledns]). 436 3. Actual "attacks" 438 A very quick examination of DNS traffic may lead to the false 439 conclusion that extracting the needle from the haystack is difficult. 440 "Interesting" primary DNS requests are mixed with useless (for the 441 eavesdropper) second and tertiary requests (see the terminology in 442 Section 1). But, in this time of "big data" processing, powerful 443 techniques now exist to get from the raw data to what you're actually 444 interested in. 446 Many research papers about malware detection use DNS traffic to 447 detect "abnormal" behaviour that can be traced back to the activity 448 of malware on infected machines. Yes, this research was done for the 449 good but, technically, it is a privacy attack and it demonstrates the 450 power of the observation of DNS traffic. See [dns-footprint], 451 [dagon-malware] and [darkreading-dns]. 453 Passive DNS systems [passive-dns] allow reconstruction of the data of 454 sometimes an entire zone. It is used for many reasons, some good, 455 some bad. It is an example of a privacy issue even when no source IP 456 address is kept. 458 4. Legalities 460 To our knowledge, there are no specific privacy laws for DNS data. 461 Interpreting general privacy laws like [data-protection-directive] 462 (European Union) in the context of DNS traffic data is not an easy 463 task and it seems there is no court precedent here. 465 5. Security considerations 467 This document is entirely about security, more precisely privacy. It 468 just lays down the problem, it does not try to set requirments (with 469 the choices and compromises they imply), much less to define 470 solutions. A document on requirments for DNS privacy is 471 [I-D.hallambaker-dnse]. Possible solutions to the issues described 472 here are discussed in other documents (currently too many to be 473 listed here). 475 6. Acknowledgments 477 Thanks to Nathalie Boulvard and to the CENTR members for the original 478 work which leaded to this document. Thanks to Ondrej Sury for the 479 interesting discussions. Thanks to Mohsen Souissi and John Heidemann 480 for proofreading, to Paul Hoffman, Marcos Sanz and Warren Kumari for 481 proofreading, technical remarks, and many readability improvements. 482 Thanks to Dan York, Suzanne Woolf, Tony Finch, Peter Koch and Frank 483 Denis for good written contributions. 485 7. References 487 7.1. Normative References 489 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 490 STD 13, RFC 1034, November 1987. 492 [RFC1035] Mockapetris, P., "Domain names - implementation and 493 specification", STD 13, RFC 1035, November 1987. 495 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 496 Requirement Levels", BCP 14, RFC 2119, March 1997. 498 [RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J., 499 Morris, J., Hansen, M., and R. Smith, "Privacy 500 Considerations for Internet Protocols", RFC 6973, July 501 2013. 503 [RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an 504 Attack", BCP 188, RFC 7258, May 2014. 506 7.2. Informative References 508 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 509 Rose, "DNS Security Introduction and Requirements", RFC 510 4033, March 2005. 512 [RFC5936] Lewis, E. and A. Hoenes, "DNS Zone Transfer Protocol 513 (AXFR)", RFC 5936, June 2010. 515 [I-D.vandergaast-edns-client-subnet] 516 Contavalli, C., Gaast, W., Leach, S., and E. Lewis, 517 "Client Subnet in DNS Requests", draft-vandergaast-edns- 518 client-subnet-02 (work in progress), July 2013. 520 [I-D.hallambaker-dnse] 521 Hallam-Baker, P., "DNS Privacy and Censorship: Use Cases 522 and Requirements.", draft-hallambaker-dnse-01 (work in 523 progress), May 2014. 525 [I-D.wouters-dane-openpgp] 526 Wouters, P., "Using DANE to Associate OpenPGP public keys 527 with email addresses", draft-wouters-dane-openpgp-02 (work 528 in progress), February 2014. 530 [I-D.hoffman-dns-terminology] 531 Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS 532 Terminology", draft-hoffman-dns-terminology-00 (work in 533 progress), November 2014. 535 [dprive] IETF, DPRIVE., "The DPRIVE working group", March 2014, 536 . 538 [denis-edns-client-subnet] 539 Denis, F., "Security and privacy issues of edns-client- 540 subnet", August 2013, . 543 [dagon-malware] 544 Dagon, D., "Corrupted DNS Resolution Paths: The Rise of a 545 Malicious Resolution Authority", 2007, . 549 [dns-footprint] 550 Stoner, E., "DNS footprint of malware", October 2010, 551 . 554 [darkreading-dns] 555 Lemos, R., "Got Malware? Three Signs Revealed In DNS 556 Traffic", May 2013, 557 . 560 [dnschanger] 561 Wikipedia, , "DNSchanger", November 2011, 562 . 564 [packetq] Dot SE, , "PacketQ, a simple tool to make SQL-queries 565 against PCAP-files", 2011, 566 . 568 [dnsmezzo] 569 Bortzmeyer, S., "DNSmezzo", 2009, 570 . 572 [prism] NSA, , "PRISM", 2007, . 575 [ditl] CAIDA, , "A Day in the Life of the Internet (DITL)", 2002, 576 . 578 [turkey-googledns] 579 Bortzmeyer, S., "Hijacking of public DNS servers in 580 Turkey, through routing", 2014, 581 . 584 [data-protection-directive] 585 Europe, , "European directive 95/46/EC on the protection 586 of individuals with regard to the processing of personal 587 data and on the free movement of such data", November 588 1995, . 591 [passive-dns] 592 Weimer, F., "Passive DNS Replication", April 2005, 593 . 595 [tor-leak] 596 Tor, , "DNS leaks in Tor", 2013, 597 . 601 [yanbin-tsudik] 602 Yanbin, L. and G. Tsudik, "Towards Plugging Privacy Leaks 603 in the Domain Name System", 2009, 604 . 606 [castillo-garcia] 607 Castillo-Perez, S. and J. Garcia-Alfaro, "Anonymous 608 Resolution of DNS Queries", 2008, 609 . 611 [fangming-hori-sakurai] 612 Fangming, , Hori, Y., and K. Sakurai, "Analysis of Privacy 613 Disclosure in DNS Query", 2007, 614 . 616 [federrath-fuchs-herrmann-piosecny] 617 Federrath, H., Fuchs, K., Herrmann, D., and C. Piosecny, 618 "Privacy-Preserving DNS: Analysis of Broadcast, Range 619 Queries and Mix-Based Protection Methods", 2011, 620 . 623 7.3. URIs 625 [1] https://developers.google.com/speed/public-dns/privacy 627 Author's Address 629 Stephane Bortzmeyer 630 AFNIC 631 1, rue Stephenson 632 Montigny-le-Bretonneux 78180 633 France 635 Phone: +33 1 39 30 83 46 636 Email: bortzmeyer+ietf@nic.fr 637 URI: http://www.afnic.fr/