For example, the setuid permission on the passwd command makes it possible for users to change passwords. A passwd command with setuid permission would resemble the following:. This special permission presents a security risk. Some determined users can find a way to maintain the permissions that are granted to them by the setuid process even after the process has finished executing.
Use a shell script, or avoid using the reserved UIDs with setuid permissions. The setgid permission is similar to the setuid permission. The process's effective group ID GID is changed to the group that owns the file, and a user is granted access based on the permissions that are granted to that group.
When the setgid permission is applied to a directory, files that were created in this directory belong to the group to which the directory belongs. The files do not belong to the group to which the creating process belongs. Any user who has write and execute permissions in the directory can create a file there.
However, the file belongs to the group that owns the directory, not to the group that the user belongs to. You should monitor your system for any unauthorized use of the setgid permission to gain superuser capabilities. A suspicious permission grants group access to such a program to an unusual group rather than to root or bin.
The sticky bit is a permission bit that protects the files within a directory. If the directory has the sticky bit set, a file can be deleted only by the file owner, the directory owner, or by a privileged user. The root user and the Primary Administrator role are examples of privileged users. For instructions, see Example When you create a file or directory, you create it with a default set of permissions.
The system defaults are open. A text file has permissions, which grants read and write permission to everyone. A directory and an executable file have permissions, which grants read, write, and execute permission to everyone. The value assigned by the umask command is subtracted from the default.
This process has the effect of denying permissions in the same way that the chmod command grants them. For example, the chmod command grants write permission to group and others.
The umask command denies write permission to group and others. The following table shows some typical umask settings and their effect on an executable file. For more information on setting the umask value, see the umask 1 man page. The chmod command enables you to change the permissions on a file. You must be superuser or the owner of a file or directory to change its permissions. Absolute Mode — Use numbers to represent file permissions. Jonathan Leffler Jonathan Leffler k gold badges silver badges bronze badges.
Carl Smotricz Carl Smotricz Berkay: yes, that is what was meant. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Stack Gives Back Safety in numbers: crowdsourcing data on nefarious IP addresses. With symbolic permissions you can add, delete, or specify the permission set you want by using the operators in the following table.
Here's an example using testfile. The second way to modify permissions with the chmod command is to use a number to specify each set of permissions for the file. Each permission is assigned a value, as the following table shows, and the total of each set of permissions provides a number for that set.
Here's an example using the testfile. All the permissions mentioned above are also assigned based on the Owner and the Groups. The value of the user can be either the name of a user on the system or the user id uid of a user on the system.
The chgrp command changes the group ownership of a file. The value of group can be the name of a group on the system or the group ID GID of a group on the system. Often when a command is executed, it will have to be executed with special privileges in order to accomplish its task.
As a regular user, you do not have read or write access to this file for security reasons, but when you change your password, you need to have the write permission to this file. The license key file used for operating in the central protection mode is received from the central protection server.
The demo key file stored on the local computer, if any, is not used. Statistics on virus events together with information on Dr. Updates to virus databases are also received from the central protection server. Web for UNIX File Servers receives updates from Doctor Web update servers, but operation of the product is managed with the local settings and a license key file received from the central protection server.
You can switch to the mobile mode only if it is allowed in the central protection server settings. Central Protection Concept. Doctor Web solutions for central protection use client-server model see the figure below. Workstations and servers are protected from threats by local anti-virus components herein, Dr. Web for UNIX File Servers installed on them, which provides for anti-virus protection of remote computers and allows connection between the workstations and the central protection server.
Figure 2. Logical structure of the Anti-virus Network.
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