Firewalls and Internet Security, Second Edition

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Firewalls and Internet Security, Second Edition
Repelling the Wily Hacker

William R. Cheswick
Steven M. Bellovin
Aviel D. Rubin!
""

Addison-Wesley

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Library of Congress Cataloging-in-Publication DataCheswick, William R.
Firewalls and Internet security: repelling the wily hacker / WilliamR. Cheswick, Steven M. Bellovin and Aviel D.Rubin—2nd ed.
p. cm.
Includes bibliographical references and index.
ISBN 02016346f6X 1. Firewalls (Computer Security) I. Bellovin, Steven M. II. Rubin,
Aviel D. III. Title.
TK5105.875.157C44 2003
005.8—dc21
Copyright © 2003 by AT&T and Lumeta Corporation
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted,
in any form, or by any means, electronic, mechanical, photocopying, recording, or otherwise, without theprior consent of the publisher. Printed in the United States of American. Published simultaneously in Canada.
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to:Pearson Education, Inc.
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Boston, MA 02116
Fax: (617) 848-7047
ISBN: 0-201-63466-X
Text printed on recycled paper∞—CRS—0706050403
Last printing, April 2023

For my mother, Ruth Cheswick, whose maiden name shall not be revealed because this is asecurity book, and for my father, Richard Reid Cheswick, who taught me about Monday
mornings, and many other things. And to Terry, Kestrel, and Lorette, who had to put up withlengthy spates of grumpy editing sessions.
—W.R.C.

To my parents, Sam and Sylvia Bellovin, for everything,
and to Diane, Rebecca, and Daniel, for all the best reasons in the world.
—S.M.BTo my wife, Ann, my favorite person in the world; and to my children, Elana,Tamara, and Benny, the three best things that ever happened to me.
—A.D.R