Comments for Does email coming from the same IP address imply that it was the same computer?

Comment from Sean on 2010-04-05

2010-04-06T04:55:18Z

Hi,
I am getting abuse emails showing my close friends Static IP address.. But i gotta doubt on my new roomate. Is it possible for my roomate to use my Friend's static IP and send abuse emails to me using our common internet connection.
[Note: we use same internet connection and same computer for internet perpose..]
Pls help me with the solution... thanks!

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Comment from John Heaney on 2010-03-02

2010-03-02T16:12:44Z

Hi Leo - your site and info has been most helpful. I think I have the answer but hopefully you can help. I have had a number of e-mail from two different people supposedly, but both mails have come from IP 86.178.233.xxx. Identical. These emails have come to me over a period of about 2 weeks. These MUST be coming from the same computer, or router. Am I right? So one e-mail couldn't be coming from Aberdeen, and one from London.

Many thanks,

John Heaney

You simply can't make that assumption. ISPs do funny things with IP addresses, particularly if they IP addresses are assigned dynamically. Not only could that single IP address have been assigned to different computers over time, but there's no guarantee that the computers are near each other. Similarly, if the IP address is of a NAT router, such as you and I might use in the home, then there could be any number of computers sharing that same IP address.

03-Mar-2010

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Comment from John on 2010-01-13

2010-01-14T07:51:52Z

I'm having the exact same issue. I've compared the malicious emails with the other emails and found that one of the IPs found in both email addresses headers is EXACTLY the same (starts with 10. and the rest of the numbers match identically). Does this prove anything?

Not really, though it might be useful with other data. All that a "10." address means is that the person is behind a router. That exact same "10." address could exist behind hundreds if not thousands of different routers.

14-Jan-2010

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Comment from Col on 2009-01-11

2009-01-11T23:20:54Z

Yes...hotmail does include at least the IP address of the router that the user was connected too, I have confirmed that when i send an email through hotmail it includes my routers IP every time without fail.

It is possible your friend sent the mails but you cant be sure, what you could do is check all the IP's of your friend and also from the person sending the malicious emails and see if there is any pattern.

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A comment on: Does email coming from the same IP address imply that it was the same computer?

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Comment from Leo Notenboom on 2007-02-25

2007-02-25T23:37:27Z

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Hash: SHA1

Actually, HotMail does occasionally include IP address of the computer
accessing the web service as the x-Originating-IP - I just confirmed it.
Not sure about other providers, but that bit of anonymity obviously
isn't guaranteed.

Leo
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Comment from Eli Coten on 2007-02-24

2007-02-24T20:50:54Z

The crucial point in this case is that it's being sent from Hotmail. Any emails sent through a web-based service will have the webmail provider's email address as the X-Originating-IP because the actual computer used to send the message is not writing the headers. The headers will be written by the server-side script on the Webmail hosting providers service.

So any email sent from a webmail service will have one of the IP addresses that resolves back to the webmail provider, and all you can deduce from it is that the spammer was connected to the same webmail server as your friend on hotmail.

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Comment from Leo Notenboom on 2007-02-24

2007-02-24T18:38:15Z

Yes, it could.

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Comment from kelly pettit on 2007-02-24

2007-02-24T08:37:37Z

I'm in a battle of the bands compitition where the winner is judged by the amount of votes they get on line. You can vote once a day from your computer. They count your IP address. I'm worried that if an office of 40 friends all vote for me, they only count as one vote if it's the same IP address. 40 different computers, 40 people voting, one vote counted. Can this happen?

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A comment on: Does email coming from the same IP address imply that it was the same computer?

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