Every e-mail has a header that stores significant
information about sender of the e-mail and the path it traversed
before reaching your mailbox. In earlier issues - we have discussed
how to read e-mail headers and various header elements. In this
issue, we shall discuss how to locate actual sender of an e-mail
and his/her geographical location.
Considering anonymous nature of Internet - this a vital piece of
information for every e-business. If you receive an e-mail from
a 'customer' with US postal address but discover that the e-mail
has been sent from an African country - you know what to do !
Users of web-based free e-mail services like Yahoo, Rediffmail,
Hotmail etc. may think that their true identity and location are
hidden. In reality - one may still find information about them by
analyzing their e-mail headers.
'Received:' Headers
Of all header elements we have discussed, 'Received:'
headers are most important for identifying sender's country. One
reason is that - 'Received:' headers are most difficult to tamper
with.
Any header element can be forged and faked ones inserted up to a
point, as the headers are just textual data, and only the headers
added by servers that you trust can be considered reliable.
Every time an e-mail moves through a new mail server, a new Received
header line (and possibly other header lines) is added to the beginning
of the headers list. This means that as you read the Received headers
from top to bottom, you are gradually moving closer to the computer/person
that sent you the e-mail.
But please note that as you read through the Received header fields
and get closer to the computer/person that sent you the e-mail,
you need to consider the possibility that the sender added one or
more false Received header lines to the list (at the time, the senders
beginning of the list) in an attempt to redirect you to another
location and prevent you from finding the true sender. But, now
that you know false header lines are possible, just stay alert.
Reading 'Received:' Header
Consider following e-mail header and its interpretation:
1. Received: from [216.136.225.35] (helo=web20024.mail.yahoo.com)
2. by arjuna.banijya.com with smtp (Exim 4.43)
3. id 1CPhNE-0002Qt-0T
4. for info@infobanc.com; Thu, 04 Nov 2004 07:09:56 -0600
5. Received: from [69.132.4.255] by web20024.mail.yahoo.com via
6. HTTP; Thu, 04 Nov 2004 05:09:53 PST
I have added line numbers for clarity and help in discussion - you
will not see such line numbers in actual e-mail heading.
Interpretation
Line 1 - 4 : Mail sever arjuna.banijya.com receives a mail
for one of its clients (info@infobanc.com)
from mail server web20024.mail.yahoo.com
which has an IP address 216.136.225.35
Line 5 - 6 : Mail server web20024.mail.yahoo.com receives
a mail from IP 69.132.4.255
By the way - IP stands for Internet Protocol. The
Internet uses a technology to interlink millions of computers in
its fold - TCP/IP. The core of this technology is called IP addressing
or Internet Protocol addressing. Every computer connected to Internet
is given a unique number for identification - called IP number.
IP number is used to verify location and activities of any computer.
Your ISP provider assigns you an IP address each time you connect
to the Internet.
It is evident from header interpretation that actual sender is the
one at the bottom of series of 'Received:' headers and the recipient
is at the top. In other words, mail server web20024.mail.yahoo.com
received an e-mail from IP address 69.132.4.255.
So IP address 69.132.4.255 is the sender of this e-mail.
Interestingly, this sender used a free web-based e-mail service
(yahoo.com) to send this e-mail - still his/her identity can be
traced using IP address 69.132.4.255 found in mail header.
Locating Sender's Country from IP Address
Spammers and fraudsters may forge many header elements
like 'From:', 'Received-date:' etc. - but it is very difficult to
change IP addresses inserted by mail servers. At best, they may
insert fake 'Received': headers to confuse recipient.
Once you locate IP address of actual sender's mail server or computer,
it is possible to locate geographical location or country.
In next issue, we shall discuss various free and paid Internet resources
available for extracting information on a given IP address.
Happy and Productive Surfing
Dr. Amit K Chatterjee
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