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Subject: Re: [docstandards-interop-tech] Doc standards interop agenda
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Folks, attached is a DocBook section sample that can be used in the
scenario. The sample was graciously provided by Michael Urban. One question: what version of DocBook should we be validating with in our examples? This one is pointing to DocBook 4.4, though 4.5 is the latest... Best regards, --Scott Michael Priestley wrote:
--
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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE section SYSTEM "http://www.docbook.org/xml/4.4/docbookx.dtd"
[
<!ENTITY smtp "SMTP">
<!ENTITY unix "UNIX">
<!ENTITY pop "POP">
<!ENTITY imap "IMAP">
<!ENTITY pgp "PGP">
<!ENTITY ssl "SSL">
]>
<!-- Sample graciously provided by Michael Urban -->
<section>
<title>Security and Privacy</title>
<para> The subject of <quote>security</quote> as it applies to mail is really two subjects. On one
hand, electronic mail can be used to spread malicious computer viruses or other programs
intended to create unauthorized access or damage to a computer system or network. On the other
hand, it is not very difficult for an unauthorized individual to <quote role="figurative"
>wire-tap</quote> unencrypted mail as it moves around the Internet, compromising the privacy
of those who are exchanging mail. It is important to remember at all times that Internet
electronic mail (and, by extension, mail internal to organizations that are connected to the
Internet) is <emphasis>inherently unreliable</emphasis> with respect to both security and
privacy. </para>
<para> In computer terminology, a <firstterm>Trojan Horse</firstterm> is a program or script that
is secretly sent along via some apparently harmless carrier, and carries out some nefarious act
when it reaches the system. While our interest here is in Trojan Horses carried with electronic
mail messages, other possibilities include CD-ROMs containing software of uncertain origin,
programs downloaded from the World Wide Web, and so on, all of which should be considered
suspect sources. When a Trojan Horse has the capability of reproducing itself, either on
multiple files on a single computer, or from one computer to another, it is termed a
<firstterm>virus</firstterm><footnote>
<para> Not all viruses are Trojan Horses, but they are most commonly disseminated through that
mechanism. Some programs, termed <firstterm>worms</firstterm>, propagate themselves around a
network by exploiting known security flaws. The distinction in terminology is sometimes a
fine one, and a single program may have Trojan Horse, virus and worm elements. </para>
</footnote> and becomes a much more public nuisance. </para>
<para> Trojan Horses are common in Internet mail because <emphasis>it is extremely easy to forge
Internet messages.</emphasis> Recall the &smtp; dialog in XREF. The only
way the &smtp; server (and, ultimately, the recipient) has of knowing who the sender of a
message is is on the basis of what it is told in this dialog, or in the message headers. It is
not hard for a programmer to construct an &smtp; client that lies about this. Thus, it is
easy to send someone a message that appears to be from a <quote role="figurative"
>trusted</quote> individual containing a Trojan Horse. </para>
<blockquote role="scenario">
<para> Evil Chris sends out a forged message to Leslie, appearing to be from Leslie's system
administrator. <quote>Here is a new update to Microsoft Word. Please execute the enclosed
installer.</quote> When the attached program file is executed, it starts up a program on the
computer that relays a transcript of every key Leslie types on that computer (including
passwords to other machines on the local network) back to Chris. </para>
</blockquote>
<para> In this scenario, the Trojan Horse is used in its classical<footnote>
<para>Beware of geeks bearing gifts!</para>
</footnote> sense: to set up a program that will be used to <quote role="figurative">open the
gates</quote> to a system protected by passwords. However, the Trojan Horse could not do its
work until Leslie executed the enclosed executable. This is important to remember: a text
message by itself cannot affect the system to which it is delivered<footnote>
<para> OK, OK, a huge text message can affect free disk space, but … </para>
</footnote>. There has to be some executable portion — an actual executable program or
script, malicious macros that are executed when an enclosure is opened by Microsoft
<productname>Word</productname>, a dangerous Java
application, or the like. A cautious user will disable any feature that allows automatic
execution or installation of mail enclosures, and will be particularly cautious about opening
mail enclosures using powerful programs like Microsoft <productname>Word</productname> or
<productname>Excel</productname>, or a &unix; shell — programs that can perform
arbitrary actions dictated by their input data, often without the user's knowledge. By contrast,
opening a JPEG image enclosure specifically using a program that does nothing but display JPEG
images is safe, demonstrating an advantage of relatively small applications with specific
functionality over large do-everything packages like <productname>Word</productname>. In
general, remembering that mail can be forged, execute <emphasis>extreme</emphasis> care when
opening mail attachments; on Microsoft operating systems, having an anti-Virus program installed
and up to date may prevent damage in case a Trojan Horse is opened by mistake. </para>
<para> Another dangerous form of mail is <quote role="figurative">phishing</quote> schemes, in
which mail is forged to look like it comes from a widely-used online business, asking the user
to click on a link and connect to a site to verify their credit card or password information.
Unfortunately, the link goes to a site whose general appearance mimics the legitimate business.
Again, regard unsolicited email with suspicion, and unsolicited mail concerning passwords or
other secret information doubly so. </para>
<para> It is also not difficult for a reasonably skilled programmer to <quote role="figurative"
>wire-tap</quote>' electronic mail (or any other unencrypted Internet communication).
&smtp;, &pop;, or &imap; conversations are inherently insecure, and one should
always assume that an eavesdropper may be intercepting the communication. Accordingly, you
should <emphasis>never</emphasis> send confidential or critical information (such as passwords)
through electronic mail without using some form of encryption. Similarly, &pop; and
&imap; communications begin with a user password are normally transmitted in the clear
(i.e., not encrypted in any way) and so is subject to similar wiretapping. If possible, one's
&pop; or &imap; password should not be the same as one's other passwords (if someone
gets the password, they will only have access to mail, not to other computers). </para>
<para> Encryption technologies can address both privacy and security concerns. There are a number
of encryption tools that can be used to secure the contents of mail; the most popular may be the
<ulink url="http://www.pgp.com">&pgp;</ulink> (Pretty Good Privacy) encryption system
and/or the closely related and compatible implementation, <ulink url="http://www.gnupg.org">
<acronym>GPG</acronym>
</ulink> (GNU Privacy Guard). These systems use a public-key encryption system to allow
cooperating users to encode mail securely, and also allows one to use a <firstterm>digital
signature</firstterm> so that a recipient can certify that a message (and its enclosures)
actually came from the individual that it claims to be from. Because both sender and receiver
must agree to use encryption systems of this type, they are less widely used than one might
hope. However, most modern mail clients now make it fairly easy to use &pgp; if the user
wishes to do so. For further reading on this topic, including instructions for setting up
encrypted mail, see <ulink url="blah">the document on &pgp; </ulink>. </para>
<para> Many &pop;/&imap; and &smtp; servers utilize the widely-used Secure Socket
Layer (&ssl;) system to encrypt their respective sessions as well. This will secure the user
password for &pop; or &imap; against wire-tap penetration. An &ssl; server starts by
sending the client a <firstterm>certificate</firstterm> by which the client can verify the
server is really the machine it claims to be (typically through a third-party certificate
authority like VeriSign), and a public encryption key that is used (through a process of private
key generation and exchange beyond the scope of this paper) to securely encrypt protocols like
&pop; and &imap;. Most recent mail client programs can be configured to use &ssl; to
encrypt at least &pop; or &imap;; some can encrypt &smtp; as well. However, since
this is not necessarily the only &smtp; session that will carry the message, the message
contents may still be intercepted unencrypted at another point in its journey to its
destination. </para>
</section>
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