This paper will look at the methods and tools used by system intruders. It will analyze the development of the hacker, his motivation, his environment and the burglar tools used for system intrusion. It will also probe the nature of the vulnerable networking environments that are the target of intrusions. More important, it will address turning the tables on these intruders with their own tools and techniques. Besides reacting to attacks, there are many opportunities to learn from the intruders and design that knowledge into new defensive solutions for securing computer based systems.Having presented the problem, the paper will present a strategy to defend and thwart such intrusions in our Increasingly networked and distributed computing and telecommunications environments.