Securing Linux: A Survival Guide for Linux Security (Version 2.0)

David Koconis

Jim Murray

Jos Purvis

Darrin Wassom

SANS PRESS

February 2003

Document Legalities

Copyright 2003 The SANS Institute.

All rights reserved. The entire contents of this publication are the property of the SANS Institute. User may not copy, reproduce, distribute, display, modify or create derivative works based upon all or any portion of this publication in any medium whether printed, electronic or otherwise , without the express written consent of the SANS Institute. Without limiting the foregoing, user may not reproduce, distribute, re-publish, display, modify, or create derivative works based upon all or any portion of this publication for purposes of teaching any computer or electronic security courses to any third party without the express written consent of the SANS Institute.

Managing Editor: Barbara H. Rietveld Publication Designer: Jos Ellauri

Library of Congress Control Number: 2003101190

Warning and Disclaimer

Every effort has been made to make this book as complete and as accurate as possible, but no warranty of fitness is implied . The information provided is on an "as is" basis. The authors and the publisher shall have neither liability nor responsibility to any person or entity with respect to any loss or damages arising from the information contained in this book.

SANS Institute enthusiastically applauds the work of these professionals and their willingness to share the lessons they have learned and the techniques they use .

AUTHORS David Koconis , Dartmouth College Jim Murray , NCCI Holdings, Inc. Jos Purvis , Veritect Darrin Wassom , Spectrum Health

CONTRIBUTING REVIEWERS Mark Austin , Cendant Mortgage Benjamin Bergersen , http://www.Bergensen.org David Bianco , Thomas Jefferson National Accelerator Facility Matthew Brown , Chick-fil-a Joel Burrow , Collegis at Valencia Community College Richard Cassi , University of California, San Diego Markus DeShon , SecureWorks, Inc. Scotte Elliott , Ohio Legislative Information Systems Diana Frederick Kirk Greaser Bob Hartwig , Zee Medical, Inc. John P. Jenkinson , Science Applications International Corporation (SAIC)

EDITORS Mitch Baker , Rose-Hulman Institute of Technology Guy Bruneau , InfoPeople Security Solutions (IPSS) John Moore , DigitalNet Government Solutions Bill Stearns , SANS Institute

Scott Johnson Joseph Ledesma, County of Sacramento, CA Rob McMillen , USMC Brian Melcher Russell Morrison , AXYS Environmental Consulting Ltd. Drew Nall , SecureWorks, Inc. Stephen Northcutt , SANS Institute Jason Orme , Fermi National Accelerator Lab Donald Pitts , Raytheon Dave Taylor , Weber State University Kevin Wilson , Systems Analyst