Guide to the Secure Configuration of Debian 11
Rules, Groups, and Values defined within the XCCDF Benchmark
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net.ipv6.conf.default.autoconf
Enable auto configuration on IPv6 interfacesValue -
net.ipv6.conf.default.forwarding
Toggle IPv6 default ForwardingValue -
Limit Network-Transmitted Configuration if Using Static IPv6 Addresses
To limit the configuration information requested from other systems and accepted from the network on a system that uses statically-configured IPv6 ...Group -
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 -
Network Related Kernel Runtime Parameters for Hosts and Routers
Certain kernel parameters should be set for systems which are acting as either hosts or routers to improve the system's ability defend against cert...Group -
net.ipv4.conf.all.accept_redirects
Disable ICMP Redirect AcceptanceValue -
net.ipv4.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.ipv4.conf.default.arp_filter
Controls whether the ARP filter is enabled or not. 1 - Allows you to have multiple network interfaces on the same subnet, and have the ARPs for ea...Value -
net.ipv4.conf.default.arp_ignore
Control the response modes for ARP queries that resolve local target IP addresses: 0 - (default): reply for any local target IP address, configure...Value -
net.ipv4.conf.all.forwarding
Toggle IPv4 ForwardingValue -
net.ipv4.conf.all.log_martians
Disable so you don't Log Spoofed Packets, Source Routed Packets, Redirect PacketsValue -
net.ipv4.conf.all.rp_filter
Enable to enforce sanity checking, also called ingress filtering or egress filtering. The point is to drop a packet if the source and destination I...Value -
net.ipv4.conf.all.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 -
net.ipv4.conf.all.shared_media
Controls whether the system can send (router) or accept (host) RFC1620 shared media redirects. <code>shared_media</code> for the interface will be ...Value -
net.ipv4.conf.default.accept_redirects
Disable ICMP Redirect Acceptance?Value -
net.ipv4.conf.default.accept_source_route
Disable IP source routing?Value -
net.ipv4.conf.default.log_martians
Disable so you don't Log Spoofed Packets, Source Routed Packets, Redirect PacketsValue -
Verify Permissions on Important Files and Directories
Permissions for many files on a system must be set restrictively to ensure sensitive information is properly protected. This section discusses impo...Group -
net.ipv4.conf.default.shared_media
Controls whether the system can send(router) or accept(host) RFC1620 shared media redirects. <code>shared_media</code> for the interface will be en...Value -
net.ipv4.icmp_echo_ignore_broadcasts
Ignore all ICMP ECHO and TIMESTAMP requests sent to it via broadcast/multicastValue -
net.ipv4.icmp_ignore_bogus_error_responses
Enable to prevent unnecessary loggingValue -
net.ipv4.tcp_invalid_ratelimit
Configure the maximal rate for sending duplicate acknowledgments in response to incoming invalid TCP packets.Value -
net.ipv4.tcp_rfc1337
Enable to enable TCP behavior conformant with RFC 1337Value -
net.ipv4.tcp_syncookies
Enable to turn on TCP SYN Cookie ProtectionValue -
Disable Accepting Packets Routed Between Local Interfaces
To set the runtime status of the <code>net.ipv4.conf.all.accept_local</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net...Rule Medium Severity -
Configure ARP filtering for All IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.conf.all.arp_filter</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.i...Rule Medium Severity -
Configure Response Mode of ARP Requests for All IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.conf.all.arp_ignore</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.i...Rule Medium Severity -
Prevent Routing External Traffic to Local Loopback on All IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.conf.all.route_localnet</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w n...Rule Medium Severity -
Configure Sending and Accepting Shared Media Redirects for All IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.conf.all.shared_media</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net...Rule Medium Severity -
Configure Sending and Accepting Shared Media Redirects by Default
To set the runtime status of the <code>net.ipv4.conf.default.shared_media</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w...Rule Medium Severity -
nftables
<code>If firewalld or iptables are being used in your environment, please follow the guidance in their respective section and pass-over the guidanc...Group -
Nftables Base Chain Hooks
The possible hooks which can be used to configure the base chain are: <code>ingress</code> (only in netdev family since Linux kernel 4.2, and inet ...Value -
Nftables Chain Names
The rules in nftables are attached to chains. Unlike in iptables, there are no predefined chains like INPUT, OUTPUT, etc. Instead, to filter pack...Value -
Nftables Base Chain Policies
This is the default verdict that will be applied to packets reaching the end of the chain (i.e, no more rules to be evaluated against). Currently ...Value -
Nftables Base Chain Priorities
Each nftables base chain is assigned a priority that defines its ordering among other base chains, flowtables, and Netfilter internal operations a...Value -
Nftables Base Chain Types
Base chains are those that are registered into the Netfilter hooks, i.e. these chains see packets flowing through the Linux TCP/IP stack. The poss...Value -
Nftables Families
Netfilter enables filtering at multiple networking levels. With iptables there is a separate tool for each level: iptables, ip6tables, arptables, ...Value -
Nftables Master configuration file
The file which contains top level configuration for nftables service, and with which, the service is started.Value -
Nftables Tables
Tables in nftables hold chains. Each table only has one address family and only applies to packets of this family. Tables can have one of six fami...Value -
SuSEfirewall2
The SuSEfirewall2 provides a managed firewall.Group -
Uncomplicated Firewall (ufw)
The Linux kernel in Ubuntu provides a packet filtering system called netfilter, and the traditional interface for manipulating netfilter are the ip...Group -
Verify ufw Enabled
Theufw
service can be enabled with the following command:$ sudo systemctl enable ufw.service
Rule Medium Severity -
Uncommon Network Protocols
The system includes support for several network protocols which are not commonly used. Although security vulnerabilities in kernel networking code ...Group -
Disable RDS Support
The Reliable Datagram Sockets (RDS) protocol is a transport layer protocol designed to provide reliable high-bandwidth, low-latency communications ...Rule Low Severity -
Disable TIPC Support
The Transparent Inter-Process Communication (TIPC) protocol is designed to provide communications between nodes in a cluster. To configure the sys...Rule Low Severity -
Wireless Networking
Wireless networking, such as 802.11 (WiFi) and Bluetooth, can present a security risk to sensitive or classified systems and networks. Wireless net...Group -
Disable Wireless Through Software Configuration
If it is impossible to remove the wireless hardware from the device in question, disable as much of it as possible through software. The following ...Group -
Disable Unused Interfaces
Network interfaces expand the attack surface of the system. Unused interfaces are not monitored or controlled, and should be disabled. <br><br> If...Group -
Transport Layer Security Support
Support for Transport Layer Security (TLS), and its predecessor, the Secure Sockets Layer (SSL), is included in Red Hat Enterprise Linux in the Ope...Group -
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 t...Group
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