Guide to the Secure Configuration of Ubuntu 22.04
Rules, Groups, and Values defined within the XCCDF Benchmark
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Remote Log Server
Specify an URI or IP address of a remote host where the log messages will be sent and stored.Value -
Ensure Logs Sent To Remote Host
To configure rsyslog to send logs to a remote log server, open <code>/etc/rsyslog.conf</code> and read and understand the last section of the file,...Rule Medium Severity -
Network Configuration and Firewalls
Most systems must be connected to a network of some sort, and this brings with it the substantial risk of network attack. This section discusses th...Group -
firewalld
The dynamic firewall daemon <code>firewalld</code> provides a dynamically managed firewall with support for network “zones” to assign a level of tr...Group -
Inspect and Activate Default firewalld Rules
Firewalls can be used to separate networks into different zones based on the level of trust the user has decided to place on the devices and traffi...Group -
antivirus_use_jit SELinux Boolean
default - Default SELinux boolean setting.
on - SELinux boolean is enabled.
off - SELinux boolean is disabled.Value -
Strengthen the Default Ruleset
The default rules can be strengthened. The system scripts that activate the firewall rules expect them to be defined in configuration files under t...Group -
IPSec Support
Support for Internet Protocol Security (IPsec) is provided with Libreswan.Group -
iptables and ip6tables
A host-based firewall called <code>netfilter</code> is included as part of the Linux kernel distributed with the system. It is activated by default...Group -
Install iptables-persistent Package
Theiptables-persistent
package can be installed with the following command:$ apt-get install iptables-persistent
Rule Medium Severity -
Install iptables Package
Theiptables
package can be installed with the following command:$ apt-get install iptables
Rule Medium Severity -
Remove iptables-persistent Package
Theiptables-persistent
package can be removed with the following command:$ apt-get remove iptables-persistent
Rule Medium Severity -
Inspect and Activate Default Rules
View the currently-enforced <code>iptables</code> rules by running the command: <pre>$ sudo iptables -nL --line-numbers</pre> The command is analog...Group -
Verify ip6tables Enabled if Using IPv6
Theip6tables
service can be enabled with the following command:$ sudo systemctl enable ip6tables.service
Rule Medium Severity -
Verify iptables Enabled
Theiptables
service can be enabled with the following command:$ sudo systemctl enable iptables.service
Rule Medium Severity -
Set Default ip6tables Policy for Incoming Packets
To set the default policy to DROP (instead of ACCEPT) for the built-in INPUT chain which processes incoming packets, add or correct the following l...Rule Medium Severity -
Set configuration for IPv6 loopback traffic
Configure the loopback interface to accept traffic. Configure all other interfaces to deny traffic to the loopback network.Rule Medium Severity -
Kernel Parameters Which Affect Networking
The <code>sysctl</code> utility is used to set parameters which affect the operation of the Linux kernel. Kernel parameters which affect networking...Group -
Set configuration for loopback traffic
Configure the loopback interface to accept traffic. Configure all other interfaces to deny traffic to the loopback network.Rule Medium Severity -
Strengthen the Default Ruleset
The default rules can be strengthened. The system scripts that activate the firewall rules expect them to be defined in the configuration files <co...Group -
Ensure ip6tables Firewall Rules Exist for All Open Ports
Any ports that have been opened on non-loopback addresses need firewall rules to govern traffic.Rule Medium Severity -
Ensure iptables Firewall Rules Exist for All Open Ports
Any ports that have been opened on non-loopback addresses need firewall rules to govern traffic.Rule Medium Severity -
Set Default iptables Policy for Incoming Packets
To set the default policy to DROP (instead of ACCEPT) for the built-in INPUT chain which processes incoming packets, add or correct the following l...Rule Medium Severity -
Set Default iptables Policy for Forwarded Packets
To set the default policy to DROP (instead of ACCEPT) for the built-in FORWARD chain which processes packets that will be forwarded from one interf...Rule Medium Severity -
Restrict ICMP Message Types
In <code>/etc/sysconfig/iptables</code>, the accepted ICMP messages types can be restricted. To accept only ICMP echo reply, destination unreachabl...Group -
Log and Drop Packets with Suspicious Source Addresses
Packets with non-routable source addresses should be rejected, as they may indicate spoofing. Because the modified policy will reject non-matching ...Group -
squid_use_tproxy SELinux Boolean
default - Default SELinux boolean setting.
on - SELinux boolean is enabled.
off - SELinux boolean is disabled.Value -
Disable IPv6 Networking Support Automatic Loading
To prevent the IPv6 kernel module (<code>ipv6</code>) from binding to the IPv6 networking stack, add the following line to <code>/etc/modprobe.d/di...Rule Medium Severity -
Disable IPv6 Addressing on All IPv6 Interfaces
To disable support for (<code>ipv6</code>) addressing on all interface add the following line to <code>/etc/sysctl.d/ipv6.conf</code> (or another f...Rule Medium Severity -
Disable IPv6 Addressing on IPv6 Interfaces by Default
To disable support for (<code>ipv6</code>) addressing on interfaces by default add the following line to <code>/etc/sysctl.d/ipv6.conf</code> (or a...Rule Medium Severity -
Configure IPv6 Settings if Necessary
A major feature of IPv6 is the extent to which systems implementing it can automatically configure their networking devices using information from ...Group -
IPV6_AUTOCONF
Toggle global IPv6 auto-configuration (only, if global forwarding is disabled)Value -
net.ipv6.conf.all.accept_ra_defrtr
Accept default router in router advertisements?Value -
net.ipv6.conf.all.accept_ra_pinfo
Accept prefix information in router advertisements?Value -
net.ipv6.conf.all.accept_ra_rtr_pref
Accept router preference in router advertisements?Value -
net.ipv6.conf.all.accept_ra
Accept all router advertisements?Value -
net.ipv6.conf.all.accept_redirects
Toggle ICMP Redirect AcceptanceValue -
net.ipv6.conf.all.accept_source_route
Trackers could be using source-routed packets to generate traffic that seems to be intra-net, but actually was created outside and has been redirec...Value -
net.ipv6.conf.all.autoconf
Enable auto configuration on IPv6 interfacesValue -
net.ipv6.conf.all.forwarding
Toggle IPv6 ForwardingValue -
net.ipv6.conf.all.max_addresses
Maximum number of autoconfigured IPv6 addressesValue -
net.ipv6.conf.all.router_solicitations
Accept all router solicitations?Value -
net.ipv6.conf.default.accept_ra_defrtr
Accept default router in router advertisements?Value -
net.ipv6.conf.default.accept_ra_pinfo
Accept prefix information in router advertisements?Value -
net.ipv6.conf.default.accept_ra_rtr_pref
Accept router preference in router advertisements?Value -
net.ipv6.conf.default.accept_ra
Accept default router advertisements by default?Value -
net.ipv6.conf.default.accept_redirects
Toggle ICMP Redirect Acceptance By DefaultValue -
net.ipv6.conf.default.accept_source_route
Trackers could be using source-routed packets to generate traffic that seems to be intra-net, but actually was created outside and has been redirec...Value -
net.ipv6.conf.default.autoconf
Enable auto configuration on IPv6 interfacesValue -
net.ipv6.conf.default.forwarding
Toggle IPv6 default ForwardingValue
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