This book follows a few typographical and stylistic conventions:
New terms are set in italic the first time they are introduced.
Whenever possible, we reference the Common Vulnerabilities and Exposures (CVE) database to allow you to obtain additional information about the vulnerabilitiesfor example, http://cve.mitre.org/cgibin/cvename.cgi?name=CAN-2004-0965.
Commands, file locations, variables, and other "computer language" instructions are set in a monospace fontfor example, GET, AllowHosts, and access-list.
We also use italic to indicate the use of a placeholder in the text. For example, in the following IOS command, you should substitute "gateway IP" with an actual IP address: ip route 0.0.0.0 0.0.0.0 gateway IP.
When a line from command, code, or log listing is too long to fit on the page, we use the code-continuation character to indicate that we wrapped the line that did not originally have a line break. Here's an example:
[View full width] Jan 28 03:15:26 [10.20.30.40] 265114: %SEC-6-IPACCESSLOGP: list 105 denied tcp 172.30.128 .12(1947) -> 10.20.1.6(80), 1 packet
We often use sidebars to describe our own experiences and to present illustrative examples. Therefore, the text in most sidebars is worded in a first person voice. Here's an example:
At Least Lock the (Screen) Door
I once encountered a network without a screened subnet or a DMZ. The DNS server resided on the internal network, which was a hub-based environment. When an attacker compromised the DNS server, he installed a sniffer and was able to glean internal passwords. If the DNS server had been on a switched screened subnet, the attacker's ability to sniff passwords would have been greatly inhibited.
Finally, within each chapter, you will encounter several Notes and Tips:
Tips are used to highlight shortcuts, convenient techniques, or tools that can make a task easier. Tips also sometimes provide recommendations on best practices you should follow.
Notes provide additional background information about a topic being described, beyond what is given in the chapter text. Often, notes are used to provide references to places you can find more information about a particular topic.