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CIS Amazon Linux 2023 Benchmark for Level 2 - Server

Rules and Groups employed by this XCCDF Profile

  • Verify Group Ownership on SSH Server Private *_key Key Files

    SSH server private keys, files that match the /etc/ssh/*_key glob, must be group-owned by ssh_keys group.
    Rule Medium Severity
  • Verify Group Ownership on SSH Server Public *.pub Key Files

    SSH server public keys, files that match the /etc/ssh/*.pub glob, must be group-owned by root group.
    Rule Medium Severity
  • Verify Owner on SSH Server config file

    To properly set the owner of /etc/ssh/sshd_config, run the command:
    $ sudo chown root /etc/ssh/sshd_config 
    Rule Medium Severity
  • Verify Ownership on SSH Server Private *_key Key Files

    SSH server private keys, files that match the /etc/ssh/*_key glob, must be owned by root user.
    Rule Medium Severity
  • Verify Ownership on SSH Server Public *.pub Key Files

    SSH server public keys, files that match the /etc/ssh/*.pub glob, must be owned by root user.
    Rule Medium Severity
  • Verify Permissions on SSH Server config file

    To properly set the permissions of /etc/ssh/sshd_config, run the command:
    $ sudo chmod 0600 /etc/ssh/sshd_config
    Rule Medium Severity
  • Verify Permissions on SSH Server Private *_key Key Files

    SSH server private keys - files that match the <code>/etc/ssh/*_key</code> glob, have to have restricted permissions. If those files are owned by the <code>root</code> user and the <code>root</code...
    Rule Medium Severity
  • Verify Permissions on SSH Server Public *.pub Key Files

    To properly set the permissions of /etc/ssh/*.pub, run the command:
    $ sudo chmod 0644 /etc/ssh/*.pub
    Rule Medium Severity
  • Configure OpenSSH Server if Necessary

    If the system needs to act as an SSH server, then certain changes should be made to the OpenSSH daemon configuration file <code>/etc/ssh/sshd_config</code>. The following recommendations can be app...
    Group
  • Set SSH Client Alive Count Max

    The SSH server sends at most <code>ClientAliveCountMax</code> messages during a SSH session and waits for a response from the SSH client. The option <code>ClientAliveInterval</code> configures time...
    Rule Medium Severity
  • Set SSH Client Alive Interval

    SSH allows administrators to set a network responsiveness timeout interval. After this interval has passed, the unresponsive client will be automatically logged out. <br> <br> To set this t...
    Rule Medium Severity
  • Disable Host-Based Authentication

    SSH's cryptographic host-based authentication is more secure than <code>.rhosts</code> authentication. However, it is not recommended that hosts unilaterally trust one another, even within an organ...
    Rule Medium Severity
  • Disable SSH Access via Empty Passwords

    Disallow SSH login with empty passwords. The default SSH configuration disables logins with empty passwords. The appropriate configuration is used if no value is set for <code>PermitEmptyPasswords<...
    Rule High Severity
  • Disable SSH Support for .rhosts Files

    SSH can emulate the behavior of the obsolete rsh command in allowing users to enable insecure access to their accounts via <code>.rhosts</code> files. <br> The default SSH configuration disables su...
    Rule Medium Severity
  • Disable SSH Root Login

    The root user should never be allowed to login to a system directly over a network. To disable root login via SSH, add or correct the following line in <code>/etc/ssh/sshd_config.d/00-compliancea...
    Rule Medium Severity
  • Disable SSH TCP Forwarding

    The <code>AllowTcpForwarding</code> parameter specifies whether TCP forwarding is permitted. To disable TCP forwarding, add or correct the following line in <code>/etc/ssh/sshd_config.d/00-compli...
    Rule Medium Severity
  • Disable X11 Forwarding

    The X11Forwarding parameter provides the ability to tunnel X11 traffic through the connection to enable remote graphic connections. SSH has the capability to encrypt remote X11 connections when SSH...
    Rule Medium Severity
  • Do Not Allow SSH Environment Options

    Ensure that users are not able to override environment variables of the SSH daemon. <br> The default SSH configuration disables environment processing. The appropriate configuration is used if no v...
    Rule Medium Severity
  • Enable PAM

    UsePAM Enables the Pluggable Authentication Module interface. If set to “yes” this will enable PAM authentication using ChallengeResponseAuthentication and PasswordAuthentication in addition to PAM...
    Rule Medium Severity
  • Enable SSH Warning Banner

    To enable the warning banner and ensure it is consistent across the system, add or correct the following line in <code>/etc/ssh/sshd_config</code>: <pre>Banner /etc/issue.net</pre> Another sectio...
    Rule Medium Severity
  • Limit Users' SSH Access

    By default, the SSH configuration allows any user with an account to access the system. There are several options available to limit which users and group can access the system via SSH. It is recom...
    Rule Unknown Severity
  • Ensure SSH LoginGraceTime is configured

    The <code>LoginGraceTime</code> parameter to the SSH server specifies the time allowed for successful authentication to the SSH server. The longer the Grace period is the more open unauthenticated ...
    Rule Medium Severity
  • Set SSH Daemon LogLevel to VERBOSE

    The <code>VERBOSE</code> parameter configures the SSH daemon to record login and logout activity. To specify the log level in SSH, add or correct the following line in <code>/etc/ssh/sshd_config....
    Rule Medium Severity
  • Set SSH authentication attempt limit

    The <code>MaxAuthTries</code> parameter specifies the maximum number of authentication attempts permitted per connection. Once the number of failures reaches half this value, additional failures ar...
    Rule Medium Severity
  • Set SSH MaxSessions limit

    The <code>MaxSessions</code> parameter specifies the maximum number of open sessions permitted from a given connection. To set MaxSessions edit <code>/etc/ssh/sshd_config</code> as follows: <pre>Ma...
    Rule Medium Severity
  • Ensure SSH MaxStartups is configured

    The MaxStartups parameter specifies the maximum number of concurrent unauthenticated connections to the SSH daemon. Additional connections will be dropped until authentication succeeds or the Login...
    Rule Medium Severity
  • X Window System

    The X Window System implementation included with the system is called X.org.
    Group
  • Disable X Windows

    Unless there is a mission-critical reason for the system to run a graphical user interface, ensure X is not set to start automatically at boot and remove the X Windows software packages. There is u...
    Group
  • Remove the X Windows Package Group

    By removing the xorg-x11-server-common package, the system no longer has X Windows installed. If X Windows is not installed then the system cannot boot into graphical user mode. This prevents the s...
    Rule Medium Severity
  • System Accounting with auditd

    The audit service provides substantial capabilities for recording system activities. By default, the service audits about SELinux AVC denials and certain types of security-relevant events such as s...
    Group
  • Ensure the audit Subsystem is Installed

    The audit package should be installed.
    Rule Medium Severity
  • Enable auditd Service

    The <code>auditd</code> service is an essential userspace component of the Linux Auditing System, as it is responsible for writing audit records to disk. The <code>auditd</code> service can be ena...
    Rule Medium Severity
  • Enable Auditing for Processes Which Start Prior to the Audit Daemon

    To ensure all processes can be audited, even those which start prior to the audit daemon, add the argument <code>audit=1</code> to the default GRUB 2 command line for the Linux operating system. Co...
    Rule Low Severity
  • Extend Audit Backlog Limit for the Audit Daemon

    To improve the kernel capacity to queue all log events, even those which occurred prior to the audit daemon, add the argument <code>audit_backlog_limit=8192</code> to the default GRUB 2 command lin...
    Rule Low Severity
  • Configure auditd Rules for Comprehensive Auditing

    The <code>auditd</code> program can perform comprehensive monitoring of system activity. This section describes recommended configuration settings for comprehensive auditing, but a full description...
    Group
  • Make the auditd Configuration Immutable

    If the <code>auditd</code> daemon is configured to use the <code>augenrules</code> program to read audit rules during daemon startup (the default), add the following line to a file with suffix <cod...
    Rule Medium Severity
  • Record Events that Modify the System's Mandatory Access Controls

    If the <code>auditd</code> daemon is configured to use the <code>augenrules</code> program to read audit rules during daemon startup (the default), add the following line to a file with suffix <cod...
    Rule Medium Severity
  • Record Events that Modify the System's Mandatory Access Controls in usr/share

    If the <code>auditd</code> daemon is configured to use the <code>augenrules</code> program to read audit rules during daemon startup (the default), add the following line to a file with suffix <cod...
    Rule Medium Severity
  • Ensure auditd Collects Information on Exporting to Media (successful)

    At a minimum, the audit system should collect media exportation events for all users and root. If the <code>auditd</code> daemon is configured to use the <code>augenrules</code> program to read aud...
    Rule Medium Severity
  • Record Events that Modify the System's Network Environment

    If the <code>auditd</code> daemon is configured to use the <code>augenrules</code> program to read audit rules during daemon startup (the default), add the following lines to a file with suffix <co...
    Rule Medium Severity
  • Record Events that Modify the System's Network Environment

    If the <code>auditd</code> daemon is configured to use the <code>augenrules</code> program to read audit rules during daemon startup (the default), add the following line to a file with suffix <cod...
    Rule Medium Severity
  • Record Attempts to Alter Process and Session Initiation Information

    The audit system already collects process information for all users and root. If the <code>auditd</code> daemon is configured to use the <code>augenrules</code> program to read audit rules during d...
    Rule Medium Severity
  • Record Events When Executables Are Run As Another User

    Verify the system generates an audit record when actions are run as another user. sudo provides users with temporary elevated privileges to perform operations, either as the superuser or another us...
    Rule Medium Severity
  • Ensure auditd Collects System Administrator Actions

    At a minimum, the audit system should collect administrator actions for all users and root. If the <code>auditd</code> daemon is configured to use the <code>augenrules</code> program to read audit ...
    Rule Medium Severity
  • Record Events that Modify User/Group Information - /etc/group

    If the <code>auditd</code> daemon is configured to use the <code>augenrules</code> program to read audit rules during daemon startup (the default), add the following lines to a file with suffix <co...
    Rule Medium Severity
  • Record Events that Modify User/Group Information - /etc/gshadow

    If the <code>auditd</code> daemon is configured to use the <code>augenrules</code> program to read audit rules during daemon startup (the default), add the following lines to a file with suffix <co...
    Rule Medium Severity
  • Record Events that Modify User/Group Information - /etc/security/opasswd

    If the <code>auditd</code> daemon is configured to use the <code>augenrules</code> program to read audit rules during daemon startup (the default), add the following lines to a file with suffix <co...
    Rule Medium Severity
  • Record Events that Modify User/Group Information - /etc/passwd

    If the <code>auditd</code> daemon is configured to use the <code>augenrules</code> program to read audit rules during daemon startup (the default), add the following lines to a file with suffix <co...
    Rule Medium Severity
  • Record Events that Modify User/Group Information - /etc/shadow

    If the <code>auditd</code> daemon is configured to use the <code>augenrules</code> program to read audit rules during daemon startup (the default), add the following lines to a file with suffix <co...
    Rule Medium Severity
  • Record Attempts to perform maintenance activities

    The Amazon Linux 2023 operating system must generate audit records for privileged activities, nonlocal maintenance, diagnostic sessions and other system-level access. Verify the operating system a...
    Rule Medium Severity

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