There are security options in every operating system and any competent sysadmin will know what they are and how to use them: you may even be able to keep up with all the service packs and patches that come out. What you probably don't know is all the potential holes in your security and the tools that will be used to try to get into your system. This book will scare you thoroughly by explaining each type of attack on your network. But it then tells you how to deal with the security hole of which each attack takes advantage. The explanations are clear and detailed and cover UNIX and Linux, Windows 95, 98 and NT (with an appendix on Windows 2000), Novell NetWare and common firewalls and mail servers too. The problem is always growing, but the coverage is reasonably up-to-date and points you at some useful resources, including the companion Web site at www.hackingexposed.com.

The obvious worry with a book like this is that it will help the crackers as much as the sysadmins it's written for. But security through obscurity is no security--and anyway all of these intrusion tools and techniques are out there on the Net already for those with the time and inclination to look for them. Learning how vulnerable your network is to password crackers and direct attacks or seeing how easily intruders can find out about your systems and take advantage of your resources--and getting a step-by-step guide to keeping them out--is your best defence. --Penny Jannifer