Newsgroups: alt.books.revews,misc.books.technical,alt.books.technical,rec.arts.books,alt.security,comp.security.misc,comp.security.unix
From: danny@cs.su.oz.au (Danny)
Subject: Book Review - Firewalls and Internet Security
Message-ID: <Cq7HJ9.GtF@ucc.su.OZ.AU>
Followup-To: comp.security.misc
Nntp-Posting-Host: staff.cs.su.oz.au
Organization: Basser Dept of Computer Science, Sydney University, Australia
Date: Sun, 22 May 1994 13:30:44 GMT

     title: Firewalls and Internet Security
          : Repelling the Wily Hacker
        by: William R. Cheswick + Steven M. Bellovin
 publisher: Addison-Wesley 1994
  subjects: computer science, networking, security
     other: 306 pages, bibliography, index
   summary: you thought you were already paranoid?

Cheswick and Bellovin have written the first book that deals
specifically with the security of whole networks rather than of
individual hosts.  Based on their experience administering the Internet
firewall at AT&T, as well as on existing papers and reports, _Firewalls
and Internet Security_ tells you how to connect a network to the
Internet without exposing all your computers to nefarious attacks.  It
begins with an introduction to security issues and a review of TCP/IP
protocols from the point of view of security, but the reader is assumed
to have a good understanding of the TCP/IP, an understanding of basic
security concepts and some knowledge of Unix.

The core of the book is a detailed look at how to set up and run a
firewall.  This begins by covering the mechanics of setting up a packet
filter, application and circuit gateways, the uses and abuses of
tunneling and the general limitations of firewalls.  A long chapter then
goes into some detail in describing the application level gateway setup
at AT&T.  Also contains a brief discussion of user authentication and a
description of useful tools such as connection libraries, network
monitors and logging programs.  (They recommend doing a lot of logging.)
Also discussed are counter-intelligence measures, decoys and lures, and
how to use standard hacking tools to test your security yourself.  The
stress throughout is on keeping things simple, in traditional Unix
style.

Cheswick and Bellovin then look at how things actually work in practice.
Here they present a general typology of network attacks, an account of
their encounter with the infamous 'Berferd' hacker in 1991, and some
statistics on penetration attempts from their logs.  I'm a bit unsure
about some of the conclusions they draw from the latter (see below), but
it's good to see some statistics being published.

To round things off there are chapters on legal issues (if you watch a
hacker instead of kicking him off at once, are you responsible for any
damage he does while using your system to connect elsewhere?) and
cryptography.  The appendix contains a list of free resources - software
packages and information sources - available to those trying to maintain
secure networks, a port by port analysis of TCP and UDP protocol
weaknesses and some suggestions for vendors and manufacturers of
networking hardware and software.

This is great stuff, and I have only one quibble.  I feel Cheswick and
Bellovin are a little too paranoid in places, not in their evaluation of
possible threats or in the precautions they suggest, but in their
evaluation of the intensity of hacking activity.  So attempts to rlogin
in to their gateway as root, while they may be "evil", are almost
certainly due to bored university undergraduates - I should think it's
the last thing a competent hacker would try.  (Of course competent
hackers probably have more sense than to attack a hardened target like
AT&T at all, let alone head on.)  Attempts to log in as guest, demo or
visitor are surely signs of cluelessness, and hardly deserve to be
labelled "attacks" or "evil".  And a graph which is supposed to show
that hackers are less active on weekends, to me suggests instead that
most of their "penetration" attempts are from company employees or
university students who don't even have net access on weekends.  Using
the term "hacker" instead of "cracker" for those up to no good is one
thing; debasing the term to include everyone capable of typing "rlogin
research.att.com -l root" is another.  It's a far cry from that to being
able to mount sequence number attacks on TCP connections.

_Firewalls and Internet Security_ has no rival; while much of the
information it provides is available elsewhere, no comparable summary
exists.  Anyone in charge of installing or administering an Internet
firewall would be insane not to get a copy.  And while some of it is
irrelevant to smaller sites, much will be useful to anyone concerned
with TCP/IP network security.  That said, it should be pointed out again
that this is not an introductory book on security; not only does it
assume a solid knowledge of internet protocols, but it doesn't deal with
anything except external network threats.  Of course anyone with
pretensions to being an Internet hacker will also want to read this book
(if only to find out why they shouldn't try to crack AT&T :-) and it can
be read just for enjoyment.  As well as being extremely informative,
_Firewalls_ is also extremely entertaining, with the authors managing to
inject some lightheartedness into their subject while still respecting
its seriousness.  I finished my copy within a day of receiving it.

--

[ Declaration of interest: I requested and received a review copy of
_Firewalls and Internet Security_ from Addison-Wesley, but have no
stake, financial or otherwise, in its success. ]

--

%T 	Firewalls and Internet Security - Repelling the Wily Hacker
%A 	William R. Cheswick
%A	Steven M. Bellovin
%I 	Addison-Wesley
%C 	Reading, MA
%D 	1994
%O 	paperback, bibliography, index
%G 	ISBN 0-201-63357-4
%P 	xiv,306pp
%K 	computer science, networking, security

Danny Yee (danny@cs.su.oz.au)
22 May 1994

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