He hacked into corporate systems, scrambled phone networks, and broke into the U.S. National Defense Warning System, as well as home computers. Obviously, the race for profits underlies some of the hacking. Another reason for so much hacking is that it's easy for someone to acquire the weapons to do it. The latest hacking tools are freely shared over the Internet. This is the information they do not want you to have.
Hackers have a variety of strategies.
With one, they take software programs developed to test a computer system's integrity, and turn them back on the system by exploiting the vulnerability exposed by the software. When they see one, they launch an attack against it. Under this assault, a targeted site is bombarded with data until it runs out of memory. The targeted system is then unresponsive to the queries of legitimate customers. Some attack scripts are written by hackers and posted on the Internet for novice hackers to use.