February 20, 2020 at 9:29:21 PM UTC
VERIFY
Anomaly
Websites
Websites
Runtime: 9.2s
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On February 20, 2020 at 9:29:21 PM UTC, http://use-application-dns.net/ presented signs of DNS tampering on AS9121 in Türkiye. This might mean that http://use-application-dns.net/ was blocked, but false positives can occur. Please explore the network measurement data below.

Failures

HTTP Experiment
null
DNS Experiment
null
Control
null

DNS Queries

Resolver:
172.253.199.5
Query:
IN A use-application-dns.net
Engine:
system
Name
Class
TTL
Type
DATA
Answer IP Info
@
IN
CNAME
use-application-dns.net
Unknown AS
@
IN
A
63.245.208.212
Unknown AS

TCP Connections

63.245.208.212:80: succeeded

HTTP Requests

URL
GET https://support.mozilla.org/en-US/kb/canary-domain-use-application-dnsnet
Response Headers
Content-Length:
39849
strict-transport-security:
max-age=31536000
X-Robots-Tag:
noodp
x-content-type-options:
nosniff
Set-Cookie:
csrftoken=Q0Bt9LQ7dmKz5PN85XyMsDw5sKYI42WjdDFV7jDEZctCP5J8IuhTFMzGde4an90C; expires=Thu, 18-Feb-2021 22:29:27 GMT; Max-Age=31449600; Path=/
Expires:
Thu, 20 Feb 2020 22:29:27 GMT
Vary:
X-Mobile, User-Agent, Cookie
Server:
meinheld/0.6.1
Connection:
keep-alive
X-Backend-Server:
sumo-prod-web-54b5fc477f-vbdbr.oregon-b.mozit.cloud
Cache-Control:
no-cache, no-store, must-revalidate, max-age=0
Date:
Thu, 20 Feb 2020 22:29:27 GMT
X-Frame-Options:
DENY
Content-Type:
text/html; charset=utf-8
x-xss-protection:
1; mode=block
Response Body



  
  



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    <article class="wiki-doc">
      <h1 class="title">Canary domain - use-application-dns.net</h1>
      
  
  
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      <p>To signal that their local DNS resolver implements special features that make the network unsuitable for DoH, network administrators may configure their networks to modify DNS requests for the following special-purpose domain called a <strong>canary domain</strong>: <strong><a href="http://use-application-dns.net">use-application-dns.net</a></strong>.
</p><p>Firefox will attempt to resolve this domain using the DNS server(s) configured in the operating system of the device, and examine the result. The result will be considered negative if:
</p>
<ul><li>A response code other than NOERROR is returned, such as NXDOMAIN (non-existent domain) or SERVFAIL
</li><li>A NOERROR response code is returned, but contains neither A nor AAAA records
</li></ul>
<p>The result will be considered positive if:
</p>
<ul><li>The query completes with NOERROR and contains A or AAAA records (or both)
</li></ul>
<p>A negative result will be a signal to disable application DNS, i.e. DoH.
</p><p>The use of this domain is specified by Mozilla, as a limited-time measure until a method for signaling the presence of DNS-based content filtering is defined and adopted by an Internet standards body.
</p>
<div class="note">Note: Some existing DNS filtering providers implement similar domains for users to verify that filtering is working. This canary domain differs by being intended to be checked by software such as Firefox, rather than checked explicitly by the user, and by working across filtering providers.</div>
    
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