Eric Cole & John M. Millican 
SANS GIAC Certification [PDF ebook] 
Security Essentials Toolkit (GSEC)

Master the tools of the network security trade with the official book from SANS Press! You need more than a hammer to build a house, and you need more than one tool to secure your network. Security Essentials Toolkit covers the critical tools that you need to secure your site, showing you why, when, and how to use them. Based on the SANS Institute’s renowned Global Information Assurance Certification (GIAC) program, this book takes a workbook-style approach that gives you hands-on experience and teaches you how to install, configure, and run the best security tools of the trade.