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It is easy to conclude that x.foo.com and y.foo.com are from the same origin. However, there are cases that a.com and b.com are also from a same origin although their domain names are different. For instance, yahoo.com and yimg.com are from the same origin, which is controlled by Yahoo. When using whois service to look up these 2 domains, it is obvious that they have same DNS servers (Name Servers):

   Name Server: NS1.YAHOO.COM
   Name Server: NS2.YAHOO.COM
   Name Server: NS3.YAHOO.COM
   Name Server: NS4.YAHOO.COM
   Name Server: NS5.YAHOO.COM

So is it correct if I say if 2 domains has identical name servers, they are from the same origin?

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Short answer: No, you cannot assume that the same name servers means the same origin due to shared hosting companies.

Longer answer: It depends on what you mean by origin, but still by and large no. There are a few possible meanings of the phrase, so I'll briefly discuss a few scenarios.

  1. Origin: Some company or organization.

The case for these not being the same includes hosting companies. Both company a (a.com) and company b (b.com) can use the same hosting company c (c.com). So it would be possible for both a.com and b.com to have the same servers of ns.c.com. However, they are still not associated with each other.

For instance: canadianlacrosse.ca and lookingforwardgivingback.com are both hosted with the same NS server, however are not associated with each other.

$ nslookup -type=NS canadianlacrosse.ca
Non-authoritative answer:
Server:  google-public-dns-a.google.com
Address:  8.8.8.8

canadianlacrosse.ca     nameserver = ns34.domaincontrol.com
canadianlacrosse.ca     nameserver = ns33.domaincontrol.com

$ nslookup -type=NS lookingforwardgivingback.com
Non-authoritative answer:
Server:  google-public-dns-a.google.com
Address:  8.8.8.8

lookingforwardgivingback.com    nameserver = ns34.domaincontrol.com
lookingforwardgivingback.com    nameserver = ns33.domaincontrol.com
  1. Origin: Same IP address

This also cannot be assumed, again due to shared hosting companies. Using the example above again, a.com could be hosted at IP address 1.1.1.1 and b.com could be hosted at IP address 2.2.2.2. The same name server does not necessarily provide any context about whence the network traffic is coming.

Using the real-world examples from above:

$ nslookup -type=A canadianlacrosse.ca
Non-authoritative answer:
Server:  google-public-dns-a.google.com
Address:  8.8.8.8

Name:    canadianlacrosse.ca
Address:  184.168.221.2

$ nslookup -type=A lookingforwardgivingback.com
Non-authoritative answer:
Server:  google-public-dns-a.google.com
Address:  8.8.8.8

Name:    lookingforwardgivingback.com
Address:  50.63.202.25

Note: It is possible for them to have the same IP address as well, for the same reason as above, shared hosting companies.

  1. Origin: Same server

Finally, we can't assume that the same name server has any bearing on if it is the same server even. This one you probably assumed, however I mention this due to the ambiguity of attempting to identify how hosting/name services work. We also can't rule out the fact that they are the same server either, at least not without a little bit of work going further.

What does it all mean? So, name services are the glue used to connect people to services. As much as actual glue doesn't give you an indication to what it is holding together, neither do name services in general. You will to think critically about which name server you are using, and what name you are looking up.

While in some cases (like the example you provided) the same server host organizationally owned domains, it is not true in all cases.

Updated based on comments:

While DNS is flexible enough to not have any inherent ownerships as part of it's configuration, common convention allows you to make inferences based on usage.

So, an authoritative name server that is owned by an organization for its own domains can usually be relied on to identify common ownership. Your example shows that.

However, this only proves common ownership, it would be a fallacy (I think this is the correct use) to say it proves lack of ownership. That is to say, two domains without the same NS can still be owned by the same organization.

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  • Actually, I am reading a paper here: web.eecs.umich.edu/~harshavm/papers/imc11.pdf And, base on your answer, the section 4.2 "Service complexity" seems to be wrong cos they wrote: "We then do an additional check and mark domains as belonging to different origins only if the authoritative name servers of the two domains do not match [33]. Because yimg.com and yahoo.com share the same authoritative name servers, we avoid classifying yimg.com as having a different origin from yahoo.com." – 4253wyerg4e Feb 5 '17 at 6:24
  • So this is related to the fact that DNS can be used in many different ways. So, given that, it is possible to use it to correlate data about servers and domains however it would still rely on some intelligence (human or otherwise). – prateek61 Feb 14 '17 at 10:43
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No.

I'm not entirely sure what you exactly what you are meaning when you say same origin (I can think of 2 possible intepretations), but it is possible for the same nameserver to host domain names with differering origins, ie example.com and toshow.org.nz can both use the same nameservers (and the nameservers can return identical or totally different record sets for the domains).

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