Jack is a Senior Instructor and Security Program Manager at InfoSec Institute, a provider of advanced ethical hacking training. He regularly is called upon to train members of the United States intelligence community, military, and federal law enforcement agencies. Additionally, Jack provides training for Fortune 500 companies, such as Microsoft, HP and Citibank on how to better secure their networks and applications. When not teaching hacking classes, Jack regularly performs penetration tests and application security assessments for a number of clients. He has years of private vulnerability development and exploitation experience for his customers and himself. Jack is the lead author of "The Shellcoder's Handbook: Discovering and Exploiting Security Holes". He is also the author of "Intrusion Detection with Snort", one of the best selling security books in its first year of publication, 2003. The book has been translated into several languages, including French and Japanese , and has received rave reviews from Linux Journal , Slashdot and Information Security Magazine. Jack has appeared in USA Today, CNN, MSNBC, First Business and other media outlets for his expert opinions on information security.