CCN Red Hat Enterprise Linux 9 - Advanced
Rules and Groups employed by this XCCDF Profile
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Network Parameters for Hosts Only
If the system is not going to be used as a router, then setting certain kernel parameters ensure that the host will not perform routing of network ...Group -
Disable Kernel Parameter for Sending ICMP Redirects on all IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.conf.all.send_redirects</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w n...Rule Medium Severity -
Disable Kernel Parameter for Sending ICMP Redirects on all IPv4 Interfaces by Default
To set the runtime status of the <code>net.ipv4.conf.default.send_redirects</code> kernel parameter, run the following command: <pre>$ sudo sysctl ...Rule Medium Severity -
Disable Kernel Parameter for IP Forwarding on IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.ip_forward</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.ip_fo...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 -
Verify nftables Service is Disabled
nftables is a subsystem of the Linux kernel providing filtering and classification of network packets/datagrams/frames and is the successor to ipta...Rule Medium Severity -
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 -
Restrict Dynamic Mounting and Unmounting of Filesystems
Linux includes a number of facilities for the automated addition and removal of filesystems on a running system. These facilities may be necessary...Group -
Disable Mounting of squashfs
To configure the system to prevent the <code>squashfs</code> kernel module from being loaded, add the following line to the file <code>/etc/modpro...Rule Low Severity -
Disable Mounting of udf
To configure the system to prevent the <code>udf</code> kernel module from being loaded, add the following line to the file <code>/etc/modprobe.d/...Rule Low Severity -
Disable Modprobe Loading of USB Storage Driver
To prevent USB storage devices from being used, configure the kernel module loading system to prevent automatic loading of the USB storage driver. ...Rule Medium Severity -
Restrict Programs from Dangerous Execution Patterns
The recommendations in this section are designed to ensure that the system's features to protect against potentially dangerous program execution ar...Group -
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,...Group -
Disable Core Dumps for SUID programs
To set the runtime status of the <code>fs.suid_dumpable</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w fs.suid_dumpable=...Rule Medium Severity -
SELinux
SELinux is a feature of the Linux kernel which can be used to guard against misconfigured or compromised programs. SELinux enforces the idea that p...Group -
Install libselinux Package
Thelibselinux
package can be installed with the following command:$ sudo dnf install libselinux
Rule High Severity -
Ensure SELinux Not Disabled in /etc/default/grub
SELinux can be disabled at boot time by an argument in <code>/etc/default/grub</code>. Remove any instances of <code>selinux=0</code> from the kern...Rule Medium Severity -
Configure SELinux Policy
The SELinux <code>targeted</code> policy is appropriate for general-purpose desktops and servers, as well as systems in many other roles. To config...Rule Medium Severity -
Ensure SELinux State is Enforcing
The SELinux state should be set to <code><xccdf-1.2:sub idref="xccdf_org.ssgproject.content_value_var_selinux_state" use="legacy"></xccdf-1.2:sub><...Rule High Severity -
Services
The best protection against vulnerable software is running less software. This section describes how to review the software which Red Hat Enterpris...Group -
DNS Server
Most organizations have an operational need to run at least one nameserver. However, there are many common attacks involving DNS server software, a...Group -
Disable DNS Server
DNS software should be disabled on any systems which does not need to be a nameserver. Note that the BIND DNS server software is not installed on R...Group -
Uninstall bind Package
The <code>named</code> service is provided by the <code>bind</code> package. The <code>bind</code> package can be removed with the following comman...Rule Low Severity -
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...Group -
Disable vsftpd if Possible
To minimize attack surface, disable vsftpd if at all possible.Group -
Uninstall vsftpd Package
Thevsftpd
package can be removed with the following command:$ sudo dnf erase vsftpd
Rule High Severity -
IMAP and POP3 Server
Dovecot provides IMAP and POP3 services. It is not installed by default. The project page at <a href="http://www.dovecot.org">http://www.dovec...Group -
Disable Cyrus IMAP
If the system does not need to operate as an IMAP or POP3 server, the Cyrus IMAP software should be removed.Group -
Uninstall cyrus-imapd Package
Thecyrus-imapd
package can be removed with the following command:$ sudo dnf erase cyrus-imapd
Rule Unknown Severity -
Disable Dovecot
If the system does not need to operate as an IMAP or POP3 server, the dovecot software should be disabled and removed.Group -
Uninstall dovecot Package
Thedovecot
package can be removed with the following command:$ sudo dnf erase dovecot
Rule Unknown Severity -
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 unpredictabl...Group -
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 se...Rule Medium Severity -
Ensure that chronyd is running under chrony user account
chrony is a daemon which implements the Network Time Protocol (NTP). It is designed to synchronize system clocks across a variety of systems and us...Rule Medium Severity -
A remote time server for Chrony is configured
<code>Chrony</code> is a daemon which implements the Network Time Protocol (NTP). It is designed to synchronize system clocks across a variety of s...Rule Medium Severity -
Obsolete Services
This section discusses a number of network-visible services which have historically caused problems for system security, and for which disabling or...Group -
Telnet
The telnet protocol does not provide confidentiality or integrity for information transmitted on the network. This includes authentication informat...Group -
Uninstall telnet-server Package
Thetelnet-server
package can be removed with the following command:$ sudo dnf erase telnet-server
Rule High Severity -
TFTP Server
TFTP is a lightweight version of the FTP protocol which has traditionally been used to configure networking equipment. However, TFTP provides littl...Group -
Uninstall tftp-server Package
Thetftp-server
package can be removed with the following command:$ sudo dnf erase tftp-server
Rule High Severity -
Proxy Server
A proxy server is a very desirable target for a potential adversary because much (or all) sensitive data for a given infrastructure may flow throug...Group -
Disable Squid if Possible
If Squid was installed and activated, but the system does not need to act as a proxy server, then it should be disabled and removed.Group -
Uninstall squid Package
Thesquid
package can be removed with the following command:$ sudo dnf erase squid
Rule Unknown Severity -
SNMP Server
The Simple Network Management Protocol allows administrators to monitor the state of network devices, including computers. Older versions of SNMP w...Group -
Disable SNMP Server if Possible
The system includes an SNMP daemon that allows for its remote monitoring, though it not installed by default. If it was installed and activated but...Group -
Uninstall net-snmp Package
The <code>net-snmp</code> package provides the snmpd service. The <code>net-snmp</code> package can be removed with the following command: <pre> $...Rule Unknown Severity -
SSH Server
The SSH protocol is recommended for remote login and remote file transfer. SSH provides confidentiality and integrity for data exchanged between tw...Group -
Configure OpenSSH Server if Necessary
If the system needs to act as an SSH server, then certain changes should be made to the OpenSSH daemon configuration file <code>/etc/ssh/sshd_confi...Group -
Set SSH Client Alive Count Max
The SSH server sends at most <code>ClientAliveCountMax</code> messages during a SSH session and waits for a response from the SSH client. The optio...Rule Medium Severity -
Set SSH Client Alive Interval
SSH allows administrators to set a network responsiveness timeout interval. After this interval has passed, the unresponsive client will be automat...Rule Medium Severity
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