What does your IP address reveal about you?

By Leo Notenboom

What exactly can someone tell from your IP address and what can they do with it? Can they find personal details or my precise geographical location?

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It’s typically very easy to find out your IP address or the IP address of someone with whom you are communicating somehow on the internet.

Unfortunately, many people believe that with an IP address, it’s possible to find out all sorts of information about the person at that connected computer.

That’s simply not the case.

Exactly how much it does expose about you specifically depends on your ISP and how their (and your) network is configured.

The very short answer? Not much.

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Finding an IP address

Visit my article What’s my IP address? and I’ll show you your IP address and a few other bits of information that web servers get whenever you visit any web page on the internet.

Many (though not all) email services will include the IP address of the machine on which email originated in the normally hidden email header information. (As I said, not all, and even for those that do, it’s often not on all messages. If it’s not there, it’s not there.)

If you make a point-to-point connection with an instant message program (typically during a file transfer), a peer-to-peer communications program (for example Skype, depending on how the connection is made), then your IP address is also available to the computer with which yours is communicating.

The very nature of how the internet works dictates that when two computers talk to each other, they must know each other’s IP addresses.

But once you’ve received an IP address, what can you tell about it?

Domains and reverse DNS

Some IP addresses are easy; they’re static (unchanging) and have a DNS name associated with them. For example, in a Windows XP Command Shell, enter the following command:

ping -a 67.225.235.59

That’s my quick-and-easy way to do what’s called a “reverse DNS lookup”. Normally, DNS maps names (like “ask-leo.com”) to IP addresses (like 67.225.235.59). In this case, it does the reverse and reports the official domain name associated with that IP address:

Pinging lw3.pugetsoundsoftware.com [67.225.235.59] with 32 bytes of data:
Reply from 67.225.235.59: bytes=32 time=94ms TTL=44

That’s the official1 domain name of the server that today houses ask-leo.com.

Knowing the domain name, you can then do a “whois” lookup. One of my favorites is that provided by domaintools.com. For example,

http://whois.domaintools.com/ask-leo.com

Will tell you that ask-leo.com is owned by some guy named Leo Notenboom with a mailing address in Woodinville, Washington.2 You’ll get the same information looking up pugetsoundsoftware.com as well – it’s that same guy.

There also exist services, typically referred to as private registration, which essentially replace all the public registration information with that of a third party, so as to keep even the basic registration information hidden.

What if the ping doesn’t work or doesn’t return a domain name? Then, things get less precise.

Read the rest of the story here..

This post is excerpted with permission from Leo Notenboom.

About Leo Notenboom

Leo A. Notenboom is the owner of Puget Sound Software, LLC and the Leo in Ask Leo!. Leo has been in the personal computer and software industry since 1979, as a software engineer, a manager of software engineers, and as a consultant. In 1983 Leo joined what was then a medium sized local company called Microsoft and spent the next 18 years in a wide variety of groups working on a wide variety of software. If you're running Microsoft Windows, if you've used a Microsoft development tool or Microsoft Money, or if you've ever purchased a ticket through Expedia, there's a good chance you've been touched by some of his work. And of course, since 2003, Leo has been answering your tech questions on Ask Leo!

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