Novell LINUX ENTERPRISE DESKTOP 11, Руководство пользователя

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In the seventies, it was argued that this method would be more secure than others due
to the relative slowness of the algorithm used, which took a few seconds to encrypt just
one password. In the meantime, however, PCs have become powerful enough to do
several hundred thousand or even millions of encryptions per second. Because of this,
encrypted passwords should not be visible to regular users (
/etc/shadow
cannot be
read by normal users). It is even more important that passwords are not easy to guess,
in case the password file becomes visible due to some error. Consequently, it is not re-
ally useful to “translate” a password like “tantalize” into “t@nt@1lz3”.
Replacing some letters of a word with similar looking numbers is not safe enough.
Password cracking programs that use dictionaries to guess words also play with substi-
tutions like that. A better way is to make up a word with no common meaning, something
that only makes sense to you personally, like the first letters of the words of a sentence
or the title of a book, such as “The Name of the Rose” by Umberto Eco. This would
give the following safe password: “TNotRbUE9”. In contrast, passwords like “beerbud-
dy” or “jasmine76” are easily guessed even by someone who has only some casual
knowledge about you.
1.1.3 The Boot Procedure
Configure your system so it cannot be booted from a floppy or from CD, either by re-
moving the drives entirely or by setting a BIOS password and configuring the BIOS to
allow booting from a hard disk only. Normally, a Linux system is started by a boot
loader, allowing you to pass additional options to the booted kernel. Prevent others
from using such parameters during boot by setting an additional password in
/boot/
grub/menu.lst
(see Chapter 9, The Boot Loader GRUB (↑Administration Guide)).
This is crucial to your system's security. Not only does the kernel itself run with
root
permissions, but it is also the first authority to grant
root
permissions at system start-
up.
1.1.4 File Permissions
As a general rule, always work with the most restrictive privileges possible for a given
task. For example, it is definitely not necessary to be
root
to read or write e-mail. If
the mail program has a bug, this bug could be exploited for an attack that acts with ex-
actly the permissions of the program when it was started. By following the above rule,
minimize the possible damage.
4 Security Guide