The authors of this volume (and there are several) begin by explaining how and why e-mail viruses work--they point the finger mainly at software that's designed for slick presentation of mail instead of for security, as well as at uninformed end users. Then, they begin to explain what various countermeasures, including antivirus software and firewalls, can do, and offer specific configuration advice. They also explore means of configuring popular e-mail servers and clients for maximum resistance to viruses. Overall, this book is carefully researched and should provide system administrators with the information--both practical and background--that they need to protect their systems from some of the more insidious threats around. --David Wall