Networking / Beginners

Linux security

Considerable effort has been put into making Linux a very secure network operating system, and those efforts are evident. When it is configured correctly, Linux is a very secure operating system, and therefore it is often used as a company's firewall server. The following are a few highlights of Linux security:

  • Resource access-As in the other network operating systems, access to resources on a Linux network is controlled through permissions. Access control lists identifying which systems and who can access what resources are held in text files such as hosts.deny and hosts.allow. Permissions for network resources and services can be assigned to an individual user or to a group of users.
  • User authentication-To access the local system resources or any network resources, user authentication, in the form of a username and a password, is required. The user account information is kept in a text file known as the /etc/passwd file in the Linux system.
    Remember To log on to a Linux server, the user must supply a valid username and password. Both of these values are case-sensitive.
  • File and directory security-The default file system used by Linux is the EXT2 file system. Like NTFS, which is used with Windows servers, EXT2 allows administrators to assign permissions to individual files and folders. These permissions are used to control who is allowed access to specific data on the server. A secure server should have permissions set on the important data in the system.

As Linux continues to grow in popularity, it will become an increasingly common sight in server rooms of organizations of all sizes. As a network administrator, you should prepare yourself for when you encounter a Linux system-not if.

Of the platforms discussed in this chapter, Unix and Linux have the most simplistic approach to file system security, although for most environments, this approach is more than sufficient. File permissions can be assigned to either the creator of a file or directory, a group, or the entity "everyone," which includes any authenticated user.

Unix and Linux have only three rights that can be assigned. These rights are listed in Table below.

File Permissions on Unix/Linux

RightDescription
ReadAllows files to be listed, opened, and read
WriteAllows files to be created, written to, or modified
ExecuteAllows files to be executed (that is, run)

The file permissions are listed to the right of the file. There first value specifies whether the file is a file (-) or a directory (d). The next three values specify the file rights for the user, the next three for the group, and the next three for the "everyone" assignment.

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In this tutorial:

  1. Network Operating Systems and Clients
  2. Network operating systems
  3. Windows NT 4
  4. Domains and workgroups
  5. Windows NT 4 authentication
  6. Windows NT 4 file and print services
  7. Windows NT 4 application support
  8. Windows NT 4 security
  9. Windows NT 4 and Windows 2000 file system security
  10. Windows 2000
  11. Windows 2000 Active Directory and domains
  12. Windows 2000 authentication
  13. Windows 2000 file and print services
  14. Windows 2000 application support
  15. Novell NetWare
  16. NDS (Novell Directory Services)
  17. NetWare authentication
  18. NetWare file and print services
  19. NetWare application support
  20. NetWare security
  21. Linux
  22. Linux file and print services
  23. Linux application support
  24. Linux security
  25. Operating system interoperability
  26. Using Windows with NetWare
  27. Using Windows and Linux servers
  28. Using NetWare and Linux servers
  29. Operating system client support
  30. NetWare server client support
  31. Linux server client support
  32. Client operating systems
  33. Local security mechanisms for Windows 95, Windows 98, and Windows Me
  34. Windows NT Workstation, Windows 2000 Professional, and Windows XP Professional
  35. Client connectivity for Windows NT Workstation, Windows 2000 Professional, and Windows XP Professional
  36. Applications for Linux
  37. Local security mechanisms for Linux
  38. Macintosh
  39. Application support for Macintosh
  40. Selecting a NIC and network configuration settings
  41. Connecting the PC to the network
  42. Testing and troubleshooting the NIC
  43. Configuring the NIC settings
  44. Configuring client systems for TCP/IP
  45. Configuring DNS server information
  46. Configuring WINS server information
  47. Using DHCP (Dynamic Host Control Protocol)
  48. Configuring clients to access servers
  49. Client software for Microsoft networks on Windows 95/98/Me
  50. Novell client software
  51. Unix/Linux client software