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Guide to the Secure Configuration of Debian 11

Rules, Groups, and Values defined within the XCCDF Benchmark

  • 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
  • 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
  • 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

    The ip6tables service can be enabled with the following command:
    $ sudo systemctl enable ip6tables.service
    Rule Medium Severity
  • Verify iptables Enabled

    The iptables 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
  • Disable Support for IPv6 Unless Needed

    Despite configuration that suggests support for IPv6 has been disabled, link-local IPv6 address auto-configuration occurs even when only an IPv4 ad...
    Group
  • net.ipv4.conf.default.secure_redirects

    Enable to prevent hijacking of routing path by only allowing redirects from gateways known in routing table. Disable to refuse acceptance of secure...
    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 the configuration files <co...
    Group
  • 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
  • IPv6

    The system includes support for Internet Protocol version 6. A major and often-mentioned improvement over IPv4 is its enormous increase in the numb...
    Group
  • 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

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