At the conceptual level, hacking is pretty straightforward. To attack personal computers through modems, for example, a hacker will start by scanning for vulnerable systems. They may use "demon dialers" or "wardialers" to make repetitive phone calls to modems on the public Internet. To find DSL or cable openings, hackers will use port-scanner programs that repeatedly "ping" IP addresses of networked systems to see if there are openings. Then, hackers will do all sorts of things next... (Photo by Dave Martin / Getty Images)