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5) #include "head.wmi" TITLE="A public TorDNSEL service"
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10) <h1>The public TorDNSEL service</h1>

11) 

12) <h2>What is the TorDNSEL?</h2>

13) 
14) <p>TorDNSEL is an active testing, DNS-based list of Tor exit nodes. Since Tor
15) supports exit policies, a network service's Tor exit list is a function of its
16) IP address and port. Unlike with traditional DNSxLs, services need to provide
17) that information in their queries.</p>
18) 
19) <p>Previous DNSELs scraped Tor's network directory for exit node IP addresses,
20) but this method fails to list nodes that don't advertise their exit address in
21) the directory. TorDNSEL actively tests through these nodes to provide a more
22) accurate list.</p> 
23) 
24) <p>The full background and rationale for TorDNSEL is described in the official

25) <a href="https://www.torproject.org/svn/trunk/doc/contrib/torel-design.txt">design

26) document</a>. The current service only supports the first query type mentioned
27) in that document.</p>
28) 
29) <h2>How can I query the public TorDNSEL service?</h2>
30) 
31) <p>Using the command line tool dig, users can ask type 1 queries like so:</p>
32) 
33) <pre>dig 209.137.169.81.6667.4.3.2.1.ip-port.exitlist.torproject.org</pre>
34) 
35) <h2>What do the received answers mean?</h2>
36) 
37) <p>A request for the A record
38) "209.137.169.81.6667.4.3.2.1.ip-port.exitlist.torproject.org" would return
39) 127.0.0.2 if there's a Tor node that can exit through 81.169.137.209 to port
40) 6667 at 1.2.3.4. If there isn't such an exit node, the DNSEL returns
41) NXDOMAIN.</p>
42) 
43) <p>Other A records inside net 127/8, except 127.0.0.1, are reserved for future
44) use and should be interpreted by clients as indicating an exit node. Queries
45) outside the DNSEL's zone of authority result in REFUSED. Ill-formed queries
46) inside its zone of authority result in NXDOMAIN.</p>
47) 
48) <h2>How do I configure software with DNSBL support?</h2>
49) 
50) <p>Users of software with built-in support for DNSBLs can configure the
51) following zone as a DNSBL:</p>
52) 
53) <pre>[service port].[reversed service
54) address].ip-port.exitlist.torproject.org</pre>
55) 
56) <p>An example for an IRC server running on port 6667 at IP address 1.2.3.4:</p>
57) <pre>6667.4.3.2.1.ip-port.exitlist.torproject.org</pre>
58) 
59) <h2>How reliable are the answers returned by TorDNSEL?</h2>
60) 
61) <p>The current public service is operating on an experimental basis and hasn't
62) been well tested by real services. Reports of erroneous answers or service
63) interruption would be appreciated. Future plans include building a fault
64) tolerant pool of DNSEL servers. TorDNSEL is currently under active
65) development.</p>
66) 
67) <h2>How can I run my own private TorDNSEL?</h2>
68) 
69) <p>You can learn all about the code for TorDNSEL by visiting the <a
70) href="http://p56soo2ibjkx23xo.onion/">official hidden service</a> through
71) Tor.</p>
72) 
73) <p>You can download the latest source release from the <a
74) href="http://p56soo2ibjkx23xo.onion/dist/tordnsel-0.0.6.tar.gz">hidden

75) service</a> or from a 
76) <a href="https://www.torproject.org/tordnsel/dist/tordnsel-0.0.6.tar.gz">
77) local mirror</a>. It's

78) probably wise to check out the current revision from the darcs repository
79) hosted on the aforementioned hidden service.</p>
80) 

81) <p>For more information or to report something useful, please email the 
82) <tt>tordnsel</tt> alias on our <a href="<page contact>">contact page</a>.</p>