01_574183 ffirs.qxd 7/23/04 10:04 AM Page i Computer Viruses FOR DUMmIES ‰ by Peter Gregory 02_574183 ftoc.qxd 7/23/04 10:03 AM Page vi 01_574183 ffirs.qxd 7/23/04 10:04 AM Page i Computer Viruses FOR DUMmIES ‰ by Peter Gregory 01_574183 ffirs.qxd 7/23/04 10:04 AM Page ii Computer Viruses For Dummies Published by Wiley Publishing, Inc. 111 River Street Hoboken, NJ 07030-5774 Copyright © 2004 by Wiley Publishing, Inc., Indianapolis, Indiana Published by Wiley Publishing, Inc., Indianapolis, Indiana Published simultaneously in Canada 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, scanning or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax(978) 646-8600. 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Library of Congress Control Number: 2004107888 ISBN: 0-7645-7418-3 Manufactured in the United States of America 10 9 8 7 6 5 4 3 2 1 10/RQ/QY/QU/IN 01_574183 ffirs.qxd 7/23/04 10:04 AM Page iii About the Author Peter H. Gregory, CISA, CISSP, discovered computers in 1976 in his first year at the University of Nevada-Reno. He was taking a FORTRAN programming course when computer programs were painstakingly typed in on punch cards (hanging chads and all). He then got a part-time computer operator job at the University computer center, where he operated the university’s mainframe computer, a Control Data Corporation CDC-6400. His insatiable curiosity about computers led him headlong into a career that began when he completed his university education. Those fancy letters behind Peter’s name: CISSP and CISA, are two professional security certifications: Certified Information Systems Security Professional and Certified Information Systems Auditor. Peter has spent the past eleven years in the wireless telecommunications industry, working in positions where he develops security policy, security architecture, secu- rity emergency response teams, and has been a security con- sultant in general. His love for personal computers has kept him attached to one or more of them for twenty years. Author’s Acknowledgments I would like to extend thanks to great folks at Trend Micro (Michael Sweeny in the U.S. and Del Gemmell in Taiwan) and Panda Software (Alan Wallace in California, Jose Javier Merchan, and especially Fernando de la Cuadra in Spain), who provided information as well as dozens of screen shots. Special thanks go to Jennifer Byrne at Symantec who provided invaluable feedback on the draft table of contents, resulting in numerous improvements. Nalleli Lopez Hosek and David Alderman read the entire draft manuscript and made numer- ous productive suggestions to make the book easier to read and understand. Thanks you two! Tim Crothers worked hard to ensure the technical accuracy of the book. Special thanks go to Eva Neumann, who provided invaluable feedback from her perspective as a non-professional com- puter user. Many thanks to my immediate and extended family for tolerating the book writing process yet again. I’d like to dedicate this book to the memory of Ralph Pratt who showed me how to teach complex subjects to non-technical people. And thanks be to God, through whom all things are possible. 01_574183 ffirs.qxd 7/23/04 10:04 AM Page iv Publisher’s Acknowledgments We’re proud of this book; please send us your comments through our online registration form located at www.dummies.com/register/. Some of the people who helped bring this book to market include the following: Acquisitions, Editorial, and Production Media Development Project Coordinator: Project Editor:Kyle Looper CourtneyMacIntyre Acquisitions Editor:Melody Layne Layout and Graphics:Andrea Dahl, Lauren Goddard, Denny Hager, Copy Editor:Barry Childs-Helton JoyceHaughey, Michael Kruzil, Technical Editor:Tim Crothers Jacque Schneider Editorial Manager:Leah P. Cameron Proofreaders: Carl William Pierce, Media Development Manager: TECHBOOKS Production Services LauraVanWinkle Indexer: Media Development Supervisor: TECHBOOKS Production Services Richard Graves Special Help Editorial Assistant:Amanda Foxworth Dru Hoskins Cartoons:Rich Tennant (www.the5thwave.com) Publishing and Editorial for Technology Dummies Richard Swadley,Vice President and Executive Group Publisher Andy Cummings,Vice President and Publisher Mary Bednarek,Executive Acquisitions Director Mary C. Corder,Editorial Director Publishing for Consumer Dummies Diane Graves Steele,Vice President and Publisher Joyce Pepple,Acquisitions Director Composition Services Gerry Fahey,Vice President of Production Services Debbie Stailey,Director of Composition Services 02_574183 ftoc.qxd 7/23/04 10:03 AM Page v Contents at a Glance Introduction.......................................................1 Part I: Evaluating Your Virus Situation ...............9 Chapter 1: Understanding Virus Risks ..................................................11 Chapter 2: Does My Computer Have a Virus? ......................................23 Chapter 3: DoesYour Computer HaveAntivirusSoftware?................33 Part II: Deploying Your Antivirus Defenses ........49 Chapter 4: Obtaining and Installing Antivirus Software .....................51 Chapter 5: Configuring Antivirus Software ..........................................75 Chapter 6: Scanning Your Computer and E-Mail .................................87 Chapter 7: Ridding Your Computer of Viruses ....................................99 Part III: Maintaining Your Vigilance ...............115 Chapter 8: Updating Antivirus Software and Signatures ..................117 Chapter 9: Installing Security Patches ................................................127 Chapter 10: Using Firewalls and Spyware Blockers ..........................153 Chapter 11: Protecting PDAs from Viruses ........................................181 Chapter 12: Incorporating Safe Computing Practices ......................189 Part IV: Looking at Viruses under the Microscope ..............................................207 Chapter 13: Viruses and the Losers Who Write Them .....................209 Chapter 14: Trojan Horses, Worms, Spam, and Hoaxes ...................221 Chapter 15: How Viruses Function and Propagate ...........................235 Part V: The Part of Tens .................................247 Chapter 16: Almost Ten Myths about Computer Viruses ................249 Chapter 17: Ten Antivirus Programs ...................................................255 Index.............................................................265 02_574183 ftoc.qxd 7/23/04 10:03 AM Page vi 02_574183 ftoc.qxd 7/23/04 10:03 AM Page vii Table of Contents Introduction .......................................................1 About This Book ........................................................................1 How This Book Is Organized .....................................................2 Part I: Evaluating Your Virus Situation ..........................2 Part II: Deploying Your Antivirus Defenses ..................2 Part III: Maintaining Your Vigilance ...............................3 Part IV: Looking at Viruses under the Microscope ......3 Part V: The Part of Tens ..................................................4 Conventions Used in This Book ...............................................4 What You’re Not to Read ...........................................................4 Meanings of the Term “Virus” ..................................................4 Foolish Assumptions .................................................................5 Icons Used in This Book ............................................................6 Where to Go from Here .............................................................7 Write to Us! .................................................................................8 Part I: Evaluating Your Virus Situation ................9 Chapter 1: Understanding Virus Risks . . . . . . . . . . . . . . 11 Assessing the Threat to Your Computer ...............................12 Which operating system are you using? .....................12 Do you install security patches? ..................................14 How many people use the computer? ........................15 How is your computer connected to the Internet? ...15 Do you have a firewall? .................................................16 High-risk activities .........................................................18 Deciding How Much Security Is Enough ...............................21 Chapter 2: Does My Computer Have a Virus? . . . . . . . . 23 Looking at Common Virus Symptoms ...................................24 Computer too slow ........................................................24 Unexplained activity ......................................................25 Crashes or hangs ...........................................................25 Will not boot ...................................................................26 Strange computer behavior ..........................................26 Too many pop-up windows ..........................................27 Finding and Fixing a Virus .......................................................28 02_574183 ftoc.qxd 7/23/04 10:03 AM Page viii viii Computer Viruses For Dummies Developing Good Habits .........................................................29 Keeping antivirus software up to date ........................30 Scan for viruses periodically ........................................30 Install security patches .................................................30 Working on good computer hygiene ...........................31 Blocking malicious network traffic with a firewall ....31 Blocking spyware ...........................................................31 Do you have a PDA? .......................................................32 Finding Out More about Viruses ............................................32 Chapter 3: DoesYour Computer Have AntivirusSoftware? . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Understanding Antivirus Software .........................................34 Looking Around for Antivirus Icons ......................................35 Look in — or hunt for — the system tray ...................35 Look on the Start menu ................................................38 Look on the desktop ......................................................40 Look at installed programs ...........................................41 Asking at Your Place of Purchase ..........................................43 Checking the Health of Your Antivirus Software ..................44 Step 1: Determining whether your antivirus software starts at bootup .........................................44 Step 2: Determining the version of antivirus software .......................................................................46 Step 3: Figuring out when the last update occurred ........................................................47 Step 4: Figuring out when the last scan occurred .....47 Part II: Deploying Your Antivirus Defenses ........49 Chapter 4: Obtaining and Installing Antivirus Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Sticking with Name Brands You Know ..................................51 Considering Important Antivirus Features ...........................53 Fee or free subscription? ..............................................53 Scanning: Manual and scheduled ................................54 Compatibility with your e-mail program ....................55 Virus-definition updates ...............................................55 Fix and recovery ............................................................56 Bundling other features ................................................57 Upgrading and Switching Brands ...........................................60 Reasons to upgrade .......................................................60 Reasons to switch brands ............................................61 Upgrading or switching brands safely ........................63