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I just discovered that my supposedly anonymous e-mail isn't so anonymous after all. My IP and host name is sent with the headers. This information exposed, what can be found out?

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It really depends on who you're using and how for "suppsedly anonymous email". There are sites dedicated to privacy that purposely strip out information from headers and don't keep logs so that even if they're served by law enforcement or have servers taken for evidence there's nothing there to collect. That said, there is some information that must be transmitted with messages, otherwise it would be considered spam and blocked. – Bart Silverstrim Sep 4 '09 at 13:00

4 Answers

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All sorts of things -- what OS your machine (or router -- whatever's directly connected to that IP address) is running, what services might be running on there, anything that can be determined by talking to the services provided on that IP address (Windows file sharing is the best one, but even a mailserver or FTP server can provide all sorts of info).

More broadly, that IP address can be correlated with other connections you make (to websites, other e-mail, etc) as a weakish identifier.

What kind of a bollocks anonmailer doesn't strip incoming received headers, though?

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up vote 1 down vote

Where you are, who your ISP is and the ISP can tell who you are. But it depends on the law in your jurisdiction who has access to this data.

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up vote 0 down vote

A few things, with some optional depending on some variables.

For sure:

  1. Your Location - Nation definitely, State probably, City sometimes.
  2. Your ISP - its name, who owns the IP address.

You can get this information on your IP at MaxMind.

Also, since they have your IP address, they could scan and probe your network - so if you have a PC directly connected to that IP address without a firewall they could potentially find out a ton of information about you; however if you are behind a firewall, and as long as they do not compromise that firewall, then you are pretty safe from this end.

Finally, somone could go to your ISP to find out more information about you (Your name, address, hours connected with that IP, etc) but this varies by law and in the US you need a subpoena or other "emergency" reason for this info.

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...or compromise the people at the ISP ;) – Oskar Duveborn Feb 2 '10 at 8:49
up vote -1 down vote

Run a whois on your own IP. Thats the only info that is publicly available. The rest would be available to law enforcement with a subpoena.

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2  
No, that's not the only info publically available, far from it. traceroute may give more information about your physical location, nmap can tell your OS, nmap can tell the open ports, etc. – bortzmeyer Sep 11 '09 at 12:11
very true.....I was thinking the context of the question was in regards to 'can the general public find my physical street address using my ip address'.... Thanks for the additional info. – cop1152 Sep 11 '09 at 16:55

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