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Guide to the Secure Configuration of Ubuntu 22.04

Rules, Groups, and Values defined within the XCCDF Benchmark

  • ufw Must rate-limit network interfaces

    The operating system must configure the uncomplicated firewall to rate-limit impacted network interfaces. Check all the services listening to the ports with the following command: <pre>$ sudo ss -...
    Rule Medium Severity
    Show

  • Disable DCCP Support

    The Datagram Congestion Control Protocol (DCCP) is a relatively new transport layer protocol, designed to support streaming media and telephony. To configure the system to prevent the <code>dccp</...
    Rule Medium Severity
    Show

  • Wireless Networking

    Wireless networking, such as 802.11 (WiFi) and Bluetooth, can present a security risk to sensitive or classified systems and networks. Wireless networking hardware is much more likely to be include...
    Group
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  • File Permissions and Masks

    Traditional Unix security relies heavily on file and directory permissions to prevent unauthorized users from reading or modifying files to which they should not have access. <br> <br> Severa...
    Group
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  • Verify that All World-Writable Directories Have Sticky Bits Set

    When the so-called 'sticky bit' is set on a directory, only the owner of a given file may remove that file from the directory. Without the sticky bit, any user with write access to a directory may ...
    Rule Medium Severity
    Show

  • Verify Permissions on /etc/audit/audit.rules

    To properly set the permissions of /etc/audit/audit.rules, run the command: 
    $ sudo chmod 0640 /etc/audit/audit.rules
    Rule Medium Severity
    Show

  • Ensure All Files Are Owned by a Group

    If any file is not group-owned by a group present in /etc/group, the cause of the lack of group-ownership must be investigated. Following this, those files should be deleted or assigned to an appro...
    Rule Medium Severity
    Show

  • Enable Kernel Parameter to Enforce DAC on Symlinks

    To set the runtime status of the <code>fs.protected_symlinks</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w fs.protected_symlinks=1</pre> To make sure that the setting is...
    Rule Medium Severity
    Show

  • Verify Group Who Owns shadow File

    To properly set the group owner of /etc/shadow, run the command: 
    $ sudo chgrp shadow /etc/shadow
    Rule Medium Severity
    Show

  • Verify User Who Owns Backup group File

    To properly set the owner of /etc/group-, run the command: 
    $ sudo chown root /etc/group-
    Rule Medium Severity
    Show

  • Verify Permissions on shadow File

    To properly set the permissions of /etc/shadow, run the command: 
    $ sudo chmod 0640 /etc/shadow
    Rule Medium Severity
    Show

  • Verify that Shared Library Directories Have Root Group Ownership

    System-wide shared library files, which are linked to executables during process load time or run time, are stored in the following directories by default: <pre>/lib /lib64 /usr/lib /usr/lib64 </pr...
    Rule Medium Severity
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  • Verify that system commands directories are group owned by root

    System commands files are stored in the following directories by default: <pre>/bin /sbin /usr/bin /usr/sbin /usr/local/bin /usr/local/sbin </pre> All these directories should be owned by the <code...
    Rule Medium Severity
    Show

  • Verify that Shared Library Directories Have Restrictive Permissions

    System-wide shared library directories, which contain are linked to executables during process load time or run time, are stored in the following directories by default: <pre>/lib /lib64 /usr/lib /...
    Rule Medium Severity
    Show

  • Verify that System Executables Have Root Ownership

    System executables are stored in the following directories by default: <pre>/bin /sbin /usr/bin /usr/libexec /usr/local/bin /usr/local/sbin /usr/sbin</pre> All files in these directories should be ...
    Rule Medium Severity
    Show

  • Remove the systemd_timesyncd Service

    The systemd_timesyncd service should not be installed.
    Rule Low Severity
    Show

  • Verify that Shared Library Files Have Root Ownership

    System-wide shared library files, which are linked to executables during process load time or run time, are stored in the following directories by default: <pre>/lib /lib64 /usr/lib /usr/lib64 </pr...
    Rule Medium Severity
    Show

  • Disable the Automounter

    The <code>autofs</code> daemon mounts and unmounts filesystems, such as user home directories shared via NFS, on demand. In addition, autofs can be used to handle removable media, and the default c...
    Rule Medium Severity
    Show

  • Restrict Access to Kernel Message Buffer

    To set the runtime status of the <code>kernel.dmesg_restrict</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w kernel.dmesg_restrict=1</pre> To make sure that the setting is...
    Rule Low Severity
    Show

  • Kernel panic on oops

    To set the runtime status of the <code>kernel.panic_on_oops</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w kernel.panic_on_oops=1</pre> To make sure that the setting is p...
    Rule Medium Severity
    Show

  • Disable Core Dumps

    A core dump file is the memory image of an executable program when it was terminated by the operating system due to errant behavior. In most cases, only software developers legitimately need to acc...
    Group
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  • Restrict Exposed Kernel Pointer Addresses Access

    To set the runtime status of the <code>kernel.kptr_restrict</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w kernel.kptr_restrict=<xccdf-1.2:sub idref="xccdf_org.ssgproject...
    Rule Medium Severity
    Show

  • Services

    The best protection against vulnerable software is running less software. This section describes how to review the software which Ubuntu 22.04 installs on a system and disable software which is not...
    Group
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  • Disable Avahi Publishing

    To prevent Avahi from publishing its records, edit <code>/etc/avahi/avahi-daemon.conf</code> and ensure the following line appears in the <code>[publish]</code> section: <pre>disable-publishing=yes...
    Rule Low Severity
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  • Enable the NTP Daemon

    The ntp service can be enabled with the following command: 
    $ sudo systemctl enable ntp.service
    Rule High Severity
    Show

  • Disable KDump Kernel Crash Analyzer (kdump)

    The <code>kdump-tools</code> service provides a kernel crash dump analyzer. It uses the <code>kexec</code> system call to boot a secondary kernel ("capture" kernel) following a system crash, which ...
    Rule Medium Severity
    Show

  • Verify Group Who Owns cron.monthly

    To properly set the group owner of /etc/cron.monthly, run the command: 
    $ sudo chgrp root /etc/cron.monthly
    Rule Medium Severity
    Show

  • Verify Owner on cron.hourly

    To properly set the owner of /etc/cron.hourly, run the command: 
    $ sudo chown root /etc/cron.hourly
    Rule Medium Severity
    Show

  • Verify Permissions on cron.weekly

    To properly set the permissions of /etc/cron.weekly, run the command: 
    $ sudo chmod 0700 /etc/cron.weekly
    Rule Medium Severity
    Show

  • Restrict at and cron to Authorized Users if Necessary

    The <code>/etc/cron.allow</code> and <code>/etc/at.allow</code> files contain lists of users who are allowed to use <code>cron</code> and at to delay execution of processes. If these files exist an...
    Group
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  • DHCP

    The Dynamic Host Configuration Protocol (DHCP) allows systems to request and obtain an IP address and other configuration parameters from a server. <br> <br> This guide recommends configuring...
    Group
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  • Minimize the DHCP-Configured Options

    Create the file <code>/etc/dhcp/dhclient.conf</code>, and add an appropriate setting for each of the ten configuration settings which can be obtained via DHCP. For each setting, do one of the follo...
    Rule Unknown Severity
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  • Uninstall bind Package

    The named service is provided by the bind package. The bind package can be removed with the following command: 
    $ apt-get remove bind
    Rule Low Severity
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  • FTP Server

    FTP is a common method for allowing remote access to files. Like telnet, the FTP protocol is unencrypted, which means that passwords and other data transmitted during the session can be captured an...
    Group
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  • Configure Firewalls to Protect the FTP Server

    By default, <code>iptables</code> blocks access to the ports used by the web server. To configure <code>iptables</code> to allow port 21 traffic, one must edit <code>/etc/sysconfig/iptables</code>...
    Rule Unknown Severity
    Show

  • Uninstall cyrus-imapd Package

    The cyrus-imapd package can be removed with the following command: 
    $ apt-get remove cyrus-imapd
    Rule Unknown Severity
    Show

  • Ensure LDAP client is not installed

    The Lightweight Directory Access Protocol (LDAP) is a service that provides a method for looking up information from a central database. The <code>lapd-utils</code> package can be removed with the ...
    Rule Low Severity
    Show

  • Mail Server Software

    Mail servers are used to send and receive email over the network. Mail is a very common service, and Mail Transfer Agents (MTAs) are obvious targets of network attack. Ensure that systems are not r...
    Group
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  • Configure System to Forward All Mail through a specific host

    Set up a relay host that will act as a gateway for all outbound email. Edit the file <code>/etc/postfix/main.cf</code> to ensure that only the following <code>relayhost</code> line appears: <pre>re...
    Rule Medium Severity
    Show

  • Uninstall nfs-kernel-server Package

    The nfs-kernel-server package can be removed with the following command: 
    $ apt-get remove nfs-kernel-server
    Rule Low Severity
    Show

  • Disable Network File Systems (netfs)

    The netfs script manages the boot-time mounting of several types of networked filesystems, of which NFS and Samba are the most common. If these filesystem types are not in use, the script can be di...
    Rule Unknown Severity
    Show

  • Uninstall rpcbind Package

    The rpcbind utility maps RPC services to the ports on which they listen. RPC processes notify rpcbind when they start, registering the ports they are listening on and the RPC program numbers they e...
    Rule Low Severity
    Show

  • Network Time Protocol

    The Network Time Protocol is used to manage the system clock over a network. Computer clocks are not very accurate, so time will drift unpredictably on unmanaged systems. Central time protocols can...
    Group
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  • The Chrony package is installed

    System time should be synchronized between all systems in an environment. This is typically done by establishing an authoritative time server or set of servers and having all systems synchronize th...
    Rule Medium Severity
    Show

  • Remove the ntp service

    The ntpd service should not be installed.
    Rule Low Severity
    Show

  • Configure Time Service Maxpoll Interval

    The <code>maxpoll</code> should be configured to <xccdf-1.2:sub idref="xccdf_org.ssgproject.content_value_var_time_service_set_maxpoll" use="legacy"></xccdf-1.2:sub> in <code>/etc/ntp.conf</code> o...
    Rule Medium Severity
    Show

  • Configure server restrictions for ntpd

    ntpd is a daemon which implements the Network Time Protocol (NTP). It is designed to synchronize system clocks across a variety of systems and use a source that is highly accurate. More information...
    Rule Medium Severity
    Show

  • Uninstall rsync Package

    The rsyncd service can be used to synchronize files between systems over network links. The <code>rsync</code> package can be removed with the following command: <pre> $ apt-get remove rsync</pre> ...
    Rule Medium Severity
    Show

  • Uninstall xinetd Package

    The xinetd package can be removed with the following command: 
    $ apt-get remove xinetd
    Rule Low Severity
    Show

  • Remove Rsh Trust Files

    The files <code>/etc/hosts.equiv</code> and <code>~/.rhosts</code> (in each user's home directory) list remote hosts and users that are trusted by the local system when using the rshd daemon. To re...
    Rule High Severity
    Show

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