CHAPTER 9 (Virtual web hosting) HOW TO SECURE YOUR COMPUTER
CHAPTER 9 HOW TO SECURE YOUR COMPUTER Linux systems also have ordinary user accounts, which are limited in what they can do. Such users are limited to saving files in their own directory within the /home directory (although the system is usually configured so that an ordinary user can read files outside the /home directory, too). But an ordinary Ubuntu user cannot delete or modify files other than those that he created or for which he has explicitly been given permission to modify by someone else. On most Linux systems, it s possible to type root at the login prompt and, after providing the correct password, actually log in as root and perform system maintenance tasks. Ubuntu is slightly different in that the root account is disabled by default, and users are instead able to borrow superuser powers whenever they re required. For this to happen, they need to provide their login password. With desktop programs, this is automatic, but at the command prompt, users need to preface commands with sudo. Although the root account is disabled, most key operating system files belong to root, which is to say that only someone with superuser powers can alter them. Ordinary users are simply unable to modify or delete these system files, as shown in Figure 9-1. This is a powerful method of protecting the operating system configuration from accidental or even deliberate damage. Note Along with the root and ordinary user accounts, there is a third type of Linux account, which is similar to a limited user account, except that it s used by the system for various tasks. These user accounts are usually invisible to ordinary users and work in the background. For example, the audio subsystem has its own user account that Ubuntu uses to access the audio hardware. The concepts of users and files are discussed in more depth in Chapter 14. ARE YOU A CRACKER OR A HACKER? Linux users are often described as hackers. This doesn t mean they maliciously break into computers or write viruses. It s simply using the word hacker in its original sense from the 1970s, when it described a computer enthusiast who was interested in exploring the capabilities of computers. Many of the people behind multinational computing corporations started out as hackers. Examples are Steve Wozniak, a cofounder of Apple Computer, and Bill Joy, cofounder of Sun Microsystems. The word hacker is believed to derive from model train enthusiasts who hacked train tracks together as part of their hobby. When computing became popular in the early 1970s, several of these enthusiasts also became interested in computing, and the term was carried across with them. However, in recent years, the media has subverted the term hacker to apply to an individual who breaks into computer systems. This was based on ignorance, and many true hackers find the comparison extremely offensive. Because of this, the term cracker was invented to clearly define an individual who maliciously attacks computers. So, don t worry if an acquaintance describes herself as a Linux hacker, or tells you that she has spent the night hacking. Many Linux types use the term as a badge of honor.