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Guide to the Secure Configuration of Debian 11

Rules, Groups, and Values defined within the XCCDF Benchmark

  • Ensure All Logs are Rotated by logrotate

    Edit the file <code>/etc/logrotate.d/syslog</code>. Find the first line, which should look like this (wrapped for clarity): <pre>/var/log/message...
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  • Ensure logrotate is Installed

    logrotate is installed by default. The <code>logrotate</code> package can be installed with the following command: <pre> $ apt-get install logrotat...
    Rule Medium Severity
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  • Ensure Logrotate Runs Periodically

    The <code>logrotate</code> utility allows for the automatic rotation of log files. The frequency of rotation is specified in <code>/etc/logrotate....
    Rule Medium Severity
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  • Configure rsyslogd to Accept Remote Messages If Acting as a Log Server

    By default, <code>rsyslog</code> does not listen over the network for log messages. If needed, modules can be enabled to allow the rsyslog daemon t...
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  • Ensure syslog-ng is Installed

    syslog-ng can be installed in replacement of rsyslog. The <code>syslog-ng-core</code> package can be installed with the following command: <pre> $ ...
    Rule Medium Severity
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  • Enable syslog-ng Service

    The <code>syslog-ng</code> service (in replacement of rsyslog) provides syslog-style logging by default on Debian. The <code>syslog-ng</code> serv...
    Rule Medium Severity
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  • Enable rsyslog to Accept Messages via TCP, if Acting As Log Server

    The <code>rsyslog</code> daemon should not accept remote messages unless the system acts as a log server. If the system needs to act as a central l...
    Rule Unknown Severity
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  • Enable rsyslog to Accept Messages via UDP, if Acting As Log Server

    The <code>rsyslog</code> daemon should not accept remote messages unless the system acts as a log server. If the system needs to act as a central l...
    Rule Unknown Severity
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  • Rsyslog Logs Sent To Remote Host

    If system logs are to be useful in detecting malicious activities, it is necessary to send logs to a remote server. An intruder who has compromised...
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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.
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  • 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
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  • 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...
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  • firewalld

    The dynamic firewall daemon <code>firewalld</code> provides a dynamically managed firewall with support for network “zones” to assign a level of tr...
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  • 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...
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  • 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...
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  • IPSec Support

    Support for Internet Protocol Security (IPsec) is provided with Libreswan.
    Group
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  • 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...
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  • 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...
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  • Verify ip6tables Enabled if Using IPv6

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

    The iptables service can be enabled with the following command: 
    $ sudo systemctl enable iptables.service
    Rule Medium Severity
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  • 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
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  • 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...
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  • 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
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  • 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
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  • 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
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  • 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
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  • 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...
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  • 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 ...
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  • 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...
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  • 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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  • 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
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  • 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
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  • 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 ...
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  • IPV6_AUTOCONF

    Toggle global IPv6 auto-configuration (only, if global forwarding is disabled)
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  • net.ipv6.conf.all.accept_ra_defrtr

    Accept default router in router advertisements?
    Value
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  • net.ipv6.conf.all.accept_ra_pinfo

    Accept prefix information in router advertisements?
    Value
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  • net.ipv6.conf.all.accept_ra_rtr_pref

    Accept router preference in router advertisements?
    Value
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  • net.ipv6.conf.all.accept_ra

    Accept all router advertisements?
    Value
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  • net.ipv6.conf.all.accept_redirects

    Toggle ICMP Redirect Acceptance
    Value
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  • 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
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  • net.ipv6.conf.all.autoconf

    Enable auto configuration on IPv6 interfaces
    Value
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  • net.ipv6.conf.all.forwarding

    Toggle IPv6 Forwarding
    Value
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  • net.ipv6.conf.all.max_addresses

    Maximum number of autoconfigured IPv6 addresses
    Value
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  • net.ipv6.conf.all.router_solicitations

    Accept all router solicitations?
    Value
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  • net.ipv6.conf.default.accept_ra_defrtr

    Accept default router in router advertisements?
    Value
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  • net.ipv6.conf.default.accept_ra_pinfo

    Accept prefix information in router advertisements?
    Value
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  • net.ipv6.conf.default.accept_ra_rtr_pref

    Accept router preference in router advertisements?
    Value
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  • net.ipv6.conf.default.accept_ra

    Accept default router advertisements by default?
    Value
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  • net.ipv6.conf.default.accept_redirects

    Toggle ICMP Redirect Acceptance By Default
    Value
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  • 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
    Show

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