To harden a router is to render it more heavily defended and more difficult to attack. Because routers (by definition) serve as points of entry into your network, it makes sense to devote extra effort to their security. Hardening Cisco Routers shows how to make adjustments to the configurations of routers from Cisco Systems to improve their resistance to attack, particularly external attack. This is essentially a book of specialised Internetwork Operating System (IOS) commands, as well as explanations of their behaviour. It'll appeal to the router administrator--employed either by an organisation's internal network staff, an outside consultancy, or a service provider--who wants to know which IOS commands he or she should add to routers' configuration files to tighten their security without a lot of hassle.

The great thing about this book is that you can approach it in either of two ways. If you just want to clamp down on your routers' security weaknesses as soon as possible, you can begin with the checklists at the end of each chapter (each of which focuses on a particular area, such as SMTP) or the big one in an appendix, which is comprehensive. These checklists include both "how" and "why" information, as exemplified by "Disable ICMP broadcasts with the no ip directed-broadcast command". If you want more information on the big picture, or want to prepare for a specific kind of attack, read the individual chapters for detailed advice on how to set IOS to behave as you want. --David Wall

Topics covered: Internetwork Operating System (IOS) commands you can use to protect Cisco Systems routers from a variety of attacks. Specialised sections deal with security assessment, auditing, access control, privileges, optional services and the legal importance of your login banners' contents.