How to backtrace emails..

Ask most people how they determine who sent them an email message and the response is

almost universally, "By the From line." Unfortunately this symptomatic of the current

confusion among internet users as to where particular messages come from and who is

spreading spam and viruses. The "From" header is little more than a courtesy to the person

receiving the message. People spreading spam and viruses are rarely courteous. In short, if

there is any question about where a particular email message came from the safe bet is to

assume the "From" header is forged.

So how do you determine where a message actually came from? You have to understand how

email messages are put together in order to backtrack an email message. SMTP is a text

based protocol for transferring messages across the internet. A series of headers are

placed in front of the data portion of the message. By examining the headers you can

usually backtrack a message to the source network, sometimes the source host. A more

detailed essay on reading email headers can be found .

If you are using Outlook or Outlook Express you can view the headers by right clicking on

the message and selecting properties or options.

Below are listed the headers of an actual spam message I received. I've changed my email

address and the name of my server for obvious reasons. I've also double spaced the headers

to make them more readable.

Return-Path: <s359dyxtt@yahoo.com>

X-Original-To: davar@example.com

Delivered-To: davar@example.com

Received: from 12-218-172-108.client.mchsi.com (12-218-172-108.client.mchsi.com

[12.218.172.108])

by mailhost.example.com (Postfix) with SMTP id 1F9B8511C7

for <davar@example.com>; Sun, 16 Nov 2003 09:50:37 -0800 (PST)

Received: from (HELO 0udjou) [193.12.169.0] by 12-218-172-108.client.mchsi.com with ESMTP

id <536806-74276>; Sun, 16 Nov 2003 19:42:31 +0200

Message-ID: <n5-l067n7z$46-z$-n@eo2.32574>

From: "Maricela Paulson" <s359dyxtt@yahoo.com>

Reply-To: "Maricela Paulson" <s359dyxtt@yahoo.com>

To: davar@example.com

Subject: STOP-PAYING For Your PAY-PER-VIEW, Movie Channels, Mature Channels...isha

Date: Sun, 16 Nov 2003 19:42:31 +0200

X-Mailer: Internet Mail Service (5.5.2650.21)

X-Priority: 3

MIME-Version: 1.0

Content-Type: multipart/alternative;

boundary="MIMEStream=_0+211404_90873633350646_4032088448"

According to the From header this message is from Maricela Paulson at s359dyxxt@yahoo.com.

I could just fire off a message to abuse@yahoo.com, but that would be waste of time. This

message didn't come from yahoo's email service.

The header most likely to be useful in determining the actual source of an email message is

the Received header. According to the top-most Received header this message was received

from the host 12-218-172-108.client.mchsi.com with the ip address of 21.218.172.108 by my

server mailhost.example.com. An important item to consider is at what point in the chain

does the email system become untrusted? I consider anything beyond my own email server to

be an unreliable source of information. Because this header was generated by my email

server it is reasonable for me to accept it at face value.

The next Received header (which is chronologically the first) shows the remote email server

accepting the message from the host 0udjou with the ip 193.12.169.0. Those of you who know

anything about IP will realize that that is not a valid host IP address. In addition, any

hostname that ends in client.mchsi.com is unlikely to be an authorized email server. This

has every sign of being a cracked client system.

Here's is where we start digging. By default Windows is somewhat lacking in network

diagnostic tools; however, you can use the tools at to do your own checking.

davar@nqh9k:[/home/davar] $whois 12.218.172.108

AT&T WorldNet Services ATT (NET-12-0-0-0-1)

12.0.0.0 - 12.255.255.255

Mediacom Communications Corp MEDIACOMCC-12-218-168-0-FLANDREAU-MN (NET-12-218-168-0-1)

12.218.168.0 - 12.218.175.255

# ARIN WHOIS database, last updated 2003-12-31 19:15

# Enter ? for additional hints on searching ARIN's WHOIS database.

I can also verify the hostname of the remote server by using nslookup, although in this

particular instance, my email server has already provided both the IP address and the

hostname.

davar@nqh9k:[/home/davar] $nslookup 12.218.172.108

Server: localhost

Address: 127.0.0.1

Name: 12-218-172-108.client.mchsi.com

Address: 12.218.172.108

Ok, whois shows that Mediacom Communications owns that netblock and nslookup confirms the

address to hostname mapping of the remote server,12-218-172-108.client.mchsi.com. If I

preface a www in front of the domain name portion and plug that into my web browser,

http://www.mchsi.com, I get Mediacom's web site.

There are few things more embarrassing to me than firing off an angry message to someone

who is supposedly responsible for a problem, and being wrong. By double checking who owns

the remote host's IP address using two different tools (whois and nslookup) I minimize the

chance of making myself look like an idiot.

A quick glance at the web site and it appears they are an ISP. Now if I copy the entire

message including the headers into a new email message and send it to abuse@mchsi.com with

a short message explaining the situation, they may do something about it.

But what about Maricela Paulson? There really is no way to determine who sent a message,

the best you can hope for is to find out what host sent it. Even in the case of a PGP

signed messages there is no guarantee that one particular person actually pressed the send

button. Obviously determining who the actual sender of an email message is much more

involved than reading the From header. Hopefully this example may be of some use to other

forum regulars.

Backtracking EMAIL Messages

Tracking email back to its source: Twisted Evil

cause i hate spammers... Evil or Very Mad