Cross-Forest SMTP Authentication |
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By David McAmis and Don Jones
04 Oct 2004 | SearchExchange.com |
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The following is tip #5 from "8 Exchange 2003 security tips in 8 minutes" excerpted from
a chapter in David McAmis and Don Jones' book, Microsoft Exchange Server 2003 Delta
Guide, published by Sams Publishing.
Return to the main page for
more tips on this topic.
Another real security concern is the process called spoofing, in which a hacker or other
user who has malicious intent pretends to be a valid Exchange user and sends e-mail messages
as if they were from that user. Identity theft is on the rise, and spoofing provides an easy
method for hackers to obtain sensitive information from users within and outside of your
organization.
Most people don't look at the e-mail address when they reply to a message. If the e-mail
appears to have come from a trusted source, users are likely to use the Reply button to
respond to it. This address is usually not the correct reply e-mail address either.
To ensure that malicious users do not spoof e-mails or send e-mails that appear to be from
someone within your organization, Exchange 2003 provides tools and methods for combating
this security risk.
First, Exchange 2003 requires authentication before it verifies a sender's name. In this
scenario, a malicious user could try to send an e-mail with a fake From address, but this
e-mail message would not go through until the user had been authenticated on Exchange and
the name presented was checked against the global address list.
Although this provides an end to spoofed e-mail messages, it can also cause problems when
you have an Exchange topology that spans multiple forests.
Remember from the architecture discussions in Chapter 2, "Architecture," that an Exchange
organization can only span a single forest. If you have multiple Exchange organizations
running in multiple forests, there is no authentication of the user and no way to check the
sender address before sending an e-mail message.
To make this particular security feature work in a multiple-forest topology, you need to
configure all the forests involved so that you can authenticate the user and check the
sender address before sending an e-mail message. This works through cross-forest SMTP
authentication.
The basic premise behind this setup is that you will configure an SMTP connector between
each of the forests that is used to authenticate and check the user that is sending the
e-mail message against the appropriate global address list.
WEB RESOURCE
For detailed instructions on configuring cross-forest SMTP authentication, go to the Delta Guide series Web site and enter article ID A030801.
Get more "8 Exchange 2003 security tips in 8 minutes." Return to the main
page.
About the authors:
David McAmis is an enterprise architect and partner in a consulting firm in Sydney,
Australia. David has written a number of books and more than 100 articles that have appeared
in magazines and journals.
Don Jones, MCSE, CTT+, is an independent consultant and founding partner of BrainCore.Net.
Don is the author of more than a dozen books and the creator and series editor of Sams
Publishing's Delta Guide series. He is also a contributing editor and columnist for
Microsoft® Certified Professional Magazine, the Microsoft technology columnist for
CertCities.com, and a speaker at technology conferences.
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