Email Tracing
Computer Forensics 252
Thomas Schwarz, S.J. 2006
Email Investigations: Overview
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Email has become a primary means of
communication.
Email can easily be forged.
Email can be abused

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Spam
Aid in committing a crime …
Threatening email, …
Email Investigations: Overview

Email evidence:
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Is in the email itself
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Header
Contents
In logs:
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Left behind as the email travels from sender to recipient.
Law enforcement uses subpoenas to follow the trace.
System ads have some logs under their control.

Notice: All fakemailing that you will be learning can be
easily traced.
Email Fundamentals


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Email travels from originating computer to the
receiving computer through email servers.
All email servers add to the header.
Use important internet services to interpret and
verify data in a header.
Email Fundamentals

Typical path of an email message:
Mail Server
Client
Mail Server
Mail Server
Client
Email Fundamentals:
Important Services

Verification of IP addresses:
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Regional Internet Registry
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APNIC (Asia Pacific Network Information Centre).
ARIN (American Registry of Internet Numbers).
LACNIC Latin American and Caribbean IP address Regional Registry.
RIPE NCC (Réseau IP Européens Network Coordination Centre).
Whois
www.samspade.org
Numerous other websites.
My Favorite.
Email Fundamentals:
Important Services
Domain Name System (DNS) translates between domain
names and IP address.
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Name to address lookup:
1.
2.
3.
4.
5.
6.
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HOSTS files can be altered.

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Parses HOSTS file.
Asks local nameserver
Local nameserver contacts nameserver responsible for domain.
If necessary, contact root nameserver.
Remote nameserver sends data back to local nameserver.
Local nameserver caches info and informs client.
You can use this as a low-tech tool to block pop-ups.
Local nameservers can/could be tricked into accepting
unsolicited data to be cached.

“Hilary for Senate” – case.
Email Fundamentals:
Important Services
Domain Name System (DNS) translates between domain
names and IP address.
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MX records in the DNS database specify the host’s or domains
mail exchanger
Can have multiple MX records, with priority attached:
MX
10
cse
MX
100
mailhost.soe.uscs.edu
Email to user@scu.edu will then be sent to user@cse.scu.edu.
If that site is down, then it will be sent to
user@mailhost.soe.ucsc.edu.
The mailer at both sites needs also be set up to accept the
messages.
Email Fundamentals

IP-Addressing Fundamentals

IP Version 4 is slowly replaced by IP
Version 6.

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IPv4: 4 digital numbers between 0 and 255.
IPv6: 8 digital numbers between 0000 and
0xffff.
Static / dynamic addresses

Dynamic addresses assigned by DHCP within a
local domain (with same leading portion of IP
address).
Email Fundamentals:
Important Services

Many organizations use Network Address
Translation.
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NAT boxes have a single visible IP.
Incoming I-packet analyzed according to address
and port number.
Forwarded to interior network with an internal IP
address.
Typically in the “private use areas”:

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10.0.0.0 – 10.255.255.255
172.16.0.0 – 172.31.255.255
192.168.0.0-192.168.255.255
Private use addresses are not valid addresses
externally.
Email Protocols:
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Email program such as outlook or
groupwise are a client application.
Needs to interact with an email server:
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Post Office Protocol (POP)
Internet Message Access Protocol (IMAP)
Microsoft’s Mail API (MAPI)
Web-based email uses a web-page as
an interface with an email server.
Email Protocols:
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A mail server stores incoming mail and
distributes it to the appropriate mail
box.
Behavior afterwards depends on type of
protocol.
Accordingly, investigation needs to be
done at server or at the workstation.
Email Protocols:
Post Office Service Protocol
Characteristics
Stores only incoming
messages.
POP
Investigation must be at the
workstation.
Stores all messages
IMAP
Copies of incoming and outgoing
messages might be stored on the
MS’ MAPI
Lotus Notes workstation or on the server or on
both.
Web-based send and HTTP
receive.
Incoming and outgoing messages
are stored on the server, but there
might be archived or copied
messages on the workstation.
Easy to spoof identity.
Email Protocols: SMTP
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Neither IMAP or POP are involved
relaying messages between servers.
Simple Mail Transfer Protocol: SMTP
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Easy.
Has several additions.
Can be spoofed:

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By using an unsecured or undersecured email
server.
By setting up your own smtp server.
Email Protocols: SMTP
How to spoof email
telnet endor.engr.scu.edu 25
220 endor.engr.scu.edu ESMTP Sendmail 8.13.5/8.13.5; Wed, 28 Dec 2005 14:58:49
- 0800
helo 129.210.16.8
250 server8.engr.scu.edu Hello dhcp-19-198.engr.scu.edu [129.210.19.198], please
d to meet you
mail from: jholliday@engr.scu.edu
250 2.1.0 jholliday@engr.scu.edu... Sender ok
rcpt to: tschwarz@scu.edu
250 2.1.5 tschwarz@scu.edu... Recipient ok
data
354 Enter mail, end with "." on a line by itself
This is a spoofed message.
.
250 2.0.0 jBSMwnTd023057 Message accepted for delivery
quit
221 2.0.0 endor.engr.scu.edu closing connection
Email Protocols: SMTP
Return-path: <jholliday@engr.scu.edu>
Received: from MGW2.scu.edu [129.210.251.18]
This looks very convincing.
by gwcl-22.scu.edu; Wed, 28 Dec 2005 15:00:29 -0800
(unverified [129.210.16.1]) by
Only hint: receivedReceived:
line givesfrom
the endor.engr.scu.edu
name of my machine.
MGW2.scu.edu
(Vircom SMTPRS
If I were to use a machine
without4.2.425.10)
a fixed IP,with
thenESMTP
you id
for <tjschwarz@scu.edu>;
can determine the <C0066443608@MGW2.scu.edu>
DHCP address from the DHCP logs.
Wed, 28 Dec 2005 15:00:29 -0800
X-Modus-BlackList: 129.210.16.1=OK;jholliday@engr.scu.edu=OK
X-Modus-Trusted: 129.210.16.1=NO
Received: from bobadilla.engr.scu.edu (bobadilla.engr.scu.edu
[129.210.18.34])
by endor.engr.scu.edu (8.13.5/8.13.5) with SMTP id jBSMwnTd023057
for tjschwarz@scu.edu; Wed, 28 Dec 2005 15:00:54 -0800
Date: Wed, 28 Dec 2005 14:58:49 -0800
From: JoAnne Holliday <jholliday@engr.scu.edu>
Message-Id: <200512282300.jBSMwnTd023057@endor.engr.scu.edu>
this is a spoofed message.
Email Protocols: SMTP
How to spoof email

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Endor will only relay messages from machines that
have properly authenticated themselves within the
last five minutes.
Subject lines etc. are part of the data segment.
However, any misspelling will put them into the body
of the message.
Email Protocols: SMTP
How to spoof email
telnet endor.engr.scu.edu 25
220 endor.engr.scu.edu ESMTP Sendmail 8.13.5/8.13.5; Wed, 28 Dec 2005 15:36:13 0800
mail from: plocatelli@scu.edu
250 2.1.0 plocatelli@scu.edu... Sender ok
rcpt to: tschwarz@scu.edu
250 2.1.5 tschwarz@scu.edu... Recipient ok
data
354 Enter mail, end with "." on a line by itself
Date: 23 Dec 05 11:22:33
From: plocatelli@scu.edu
To: tschwarz@scu.edu
Subject: Congrats
You are hrby appointed the next president of Santa Clara University, effectively
immediately.
Best, Paul
.
250 2.0.0 jBSNaDlu023813 Message accepted for delivery
quit
Email Protocols: SMTP
How to spoof email
Email Protocols: SMTP
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Things are even easier with Windows XP.
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Turn on the SMTP service that each WinXP machine runs.
Create a file that follows the SMTP protocol.
Place the file in Inetpub/mailroot/Pickup
Email Protocols: SMTP
From HolyFather@vatican.va Tue Dec 23 17:25:50 2003
Return-Path: <HolyFather@vatican.va>
To: tschwarz@engr.scu.edu
Received: from Xavier (dhcp-19-226.engr.scu.edu [129.210.19.226])
From: HolyFather@vatican.va
by server4.engr.scu.edu (8.12.10/8.12.10) with ESMTP id hBO1Plpv027244
for <tschwarz@engr.scu.edu>; Tue, 23 Dec 2003 17:25:50 -0800
Received:
from mail pickup service by Xavier with Microsoft SMTPSVC;
This is a spoofed
message.
Tue, 23 Dec 2003 17:25:33 -0800
To: tschwarz@engr.scu.edu
From: HolyFather@vatican.va
Message-ID: <XAVIERZRTHEQXHcJcKJ00000001@Xavier>
X-OriginalArrivalTime: 24 Dec 2003 01:25:33.0942 (UTC) FILETIME=[D3B56160:01C3C9
BC]
Date: 23 Dec 2003 17:25:33 -0800
X-Spam-Checker-Version: SpamAssassin 2.60-rc3 (1.202-2003-08-29-exp) on
server4.engr.scu.edu
X-Spam-Level:
X-Spam-Status: No, hits=0.3 required=5.0 tests=NO_REAL_NAME autolearn=no
version=2.60-rc3
This is a spoofed message.
Email Protocols: SMTP
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SMTP Headers:
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Each mail-server adds to headers.
Additions are being made at the top of the
list.
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Therefore, read the header from the bottom.
To read headers, you usually have to
enable them in your mail client.
SMTP Headers
To enable headers:
 Eudora:
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Hotmail:
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Select message and go to options.
Yahoo!:
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Options  Show Headers
MS Outlook:
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Options  Preferences  Message Headers.
Juno:
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Use the Blah Blah Blah button
Mail Options  General Preferences  Show all headers.
Groupwise:

Message itself is “attached” to each email. You need to look at it.
SMTP Headers
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Headers consists of header fields
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Originator fields
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Destination address fields
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Message-ID-field is optional, but extremely important for
tracing emails through email server logs.
Informational Fields
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To, cc, bcc
Identification Fields
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from, sender, reply-to
Subject, comments, keywords
Resent Fields
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Resent fields are strictly speaking optional, but luckily, most
servers add them.
Resent-date, resent-from, resent-sender, resent-to, resent-cc,
resent-bcc, resent-msg-id
SMTP Headers
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Trace Fields
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Core of email tracing.
Regulated in RFC2821.
When a SMTP server receives a message
for delivery or forwarding, it MUST insert
trace information at the beginning of the
header.
SMTP Headers
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The FROM field, which must be supplied in an SMTP
environment, should contain both (1) the name of
the source host as presented in the EHLO command
and (2) an address literal containing the IP address
of the source, determined from the TCP connection.
The ID field may contain an "@" as suggested in RFC
822, but this is not required.
The FOR field MAY contain a list of <path> entries
when multiple RCPT commands have been given.
A server making a final delivery inserts a
return-path line.
SMTP Header
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Spotting spoofed messages
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Contents usually gives a hint.
Each SMTP server application adds a different set
of headers or structures them in a different way.
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Use internet services in order to verify header
data.
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A good investigator knows these formats.
However, some companies can outsource email or use
internal IP addresses.
Look for breaks / discrepancies in the “Received”
lines.
SMTP Header
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Investigation of spoofed messages
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Verify all IP addresses
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Keeping in mind that some addresses might be
internal addresses.
Make a time-line of events.
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Change times to universal standard time.
Look for strange behavior.
Keep clock drift in mind.
Server Logs
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E-mail logs usually identify email
messages by:
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Account received
IP address from which they were sent.
Time and date (beware of clock drift)
IP addresses
Server Logs
Dec 31 18:26:15 endor sendmail[30597]: k012OV1i030597: from=evil@evil.com, size=147,
class=0, nrcpts=1, msgid=<200601010225.k012OV1i030597@endor.engr.scu.edu>,
proto=SMTP, daemon=MTA, relay=c-24-12-227-211.hsd1.il.comcast.net [24.12.227.211]
Dec 31 18:26:15 endor spamd[28512]: spamd: connection from localhost [127.0.0.1] at port
42865
Dec 31 18:26:15 endor spamd[28512]: spamd: setuid to tschwarz succeeded
Dec 31 18:26:15 endor spamd[28512]: spamd: processing message
<200601010225.k012OV1i030597@endor.engr.scu.edu> for tschwarz:1875
Dec 31 18:26:15 endor spamd[28512]: spamd: clean message (4.6/5.0) for tschwarz:1875 in
0.2 seconds, 525 bytes.
Dec 31 18:26:15 endor spamd[28512]: spamd: result: . 4 MSGID_FROM_MTA_ID,RCVD_IN_NJABL_DUL,RCVD_IN_SORBS_DUL
scantime=0.2,size=525,user=tschwarz,uid=1875,required_score=5.0,rhost=localhost,raddr
=127.0.0.1,rport=42865,mid=<200601010225.k012OV1i030597@endor.engr.scu.edu>,auto
learn=no
Dec 31 18:26:15 endor spamd[21352]: prefork: child states: II
Dec 31 18:26:15 endor sendmail[30726]: k012OV1i030597: to=tschwarz@engr.scu.edu,
delay=00:01:02, xdelay=00:00:00, mailer=local, pri=30464, dsn=2.0.0, stat=Sent
Sample log entry at endor.
Server Logs
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Many servers keep copies of emails.
Most servers purge logs.
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Law-enforcement:
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Vast majority of companies are very cooperative.
Don’t wait for the subpoena, instead give system
administrator a heads-up of a coming subpoena.
Company:
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Local sys-ad needs early warning.
Getting logs at other places can be dicey.
Unix Sendmail
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Configuration file /etc/sendmail.cf and
/etc/syslog.conf
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maillog (often at /var/log/maillog)
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Gives location of various logs and their rules.
Logs SMTP communications
Logs POP3 events
You can always use: locate *.log to find log
files.