Australian Cyber Security Centre (ACSC) ISM Official
Rules and Groups employed by this XCCDF Profile
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Verify that System Executables Have Root Ownership
System executables are stored in the following directories by default: <pre>/bin /sbin /usr/bin /usr/libexec /usr/local/bin /usr/local/sbin /usr/sbin</pre> All files in these directories should be ...Rule Medium Severity -
Verify that Shared Library Files Have Root Ownership
System-wide shared library files, which are linked to executables during process load time or run time, are stored in the following directories by default: <pre>/lib /lib64 /usr/lib /usr/lib64 </pr...Rule Medium Severity -
Verify that System Executables Have Restrictive Permissions
System executables are stored in the following directories by default: <pre>/bin /sbin /usr/bin /usr/libexec /usr/local/bin /usr/local/sbin /usr/sbin</pre> All files in these directories should not...Rule Medium Severity -
Verify that Shared Library Files Have Restrictive Permissions
System-wide shared library files, which are linked to executables during process load time or run time, are stored in the following directories by default: <pre>/lib /lib64 /usr/lib /usr/lib64 </pr...Rule Medium Severity -
Restrict Partition Mount Options
System partitions can be mounted with certain options that limit what files on those partitions can do. These options are set in the <code>/etc/fstab</code> configuration file, and can be used to m...Group -
Add nodev Option to /dev/shm
The <code>nodev</code> mount option can be used to prevent creation of device files in <code>/dev/shm</code>. Legitimate character and block devices should not exist within temporary directories li...Rule Medium Severity -
Add noexec Option to /dev/shm
The <code>noexec</code> mount option can be used to prevent binaries from being executed out of <code>/dev/shm</code>. It can be dangerous to allow the execution of binaries from world-writable tem...Rule Medium Severity -
Add nosuid Option to /dev/shm
The <code>nosuid</code> mount option can be used to prevent execution of setuid programs in <code>/dev/shm</code>. The SUID and SGID permissions should not be required in these world-writable dire...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 are activated. These protections are applied at the ...Group -
Restrict Access to Kernel Message Buffer
To set the runtime status of the <code>kernel.dmesg_restrict</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w kernel.dmesg_restrict=1</pre> To make sure that the setting is...Rule Low Severity -
Disable Kernel Image Loading
To set the runtime status of the <code>kernel.kexec_load_disabled</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w kernel.kexec_load_disabled=1</pre> To make sure that the ...Rule Medium Severity -
Disable Access to Network bpf() Syscall From Unprivileged Processes
To set the runtime status of the <code>kernel.unprivileged_bpf_disabled</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w kernel.unprivileged_bpf_disabled=1</pre> To make su...Rule Medium Severity -
Restrict usage of ptrace to descendant processes
To set the runtime status of the <code>kernel.yama.ptrace_scope</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w kernel.yama.ptrace_scope=1</pre> To make sure that the sett...Rule Medium Severity -
Harden the operation of the BPF just-in-time compiler
To set the runtime status of the <code>net.core.bpf_jit_harden</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.core.bpf_jit_harden=2</pre> To make sure that the settin...Rule Medium Severity -
Enable ExecShield
ExecShield describes kernel features that provide protection against exploitation of memory corruption errors such as buffer overflows. These features include random placement of the stack and othe...Group -
Restrict Exposed Kernel Pointer Addresses Access
To set the runtime status of the <code>kernel.kptr_restrict</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w kernel.kptr_restrict=<xccdf-1.2:sub idref="xccdf_org.ssgproject...Rule Medium Severity -
Enable Randomized Layout of Virtual Address Space
To set the runtime status of the <code>kernel.randomize_va_space</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w kernel.randomize_va_space=2</pre> To make sure that the se...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 programs should be limited in what files they can a...Group -
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 configure the system to use this policy, add or correct ...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></code> at system boot time. In the file <code>/et...Rule High Severity -
SELinux - Booleans
Enable or Disable runtime customization of SELinux system policies without having to reload or recompile the SELinux policy.Group -
Services
The best protection against vulnerable software is running less software. This section describes how to review the software which Oracle Linux 9 installs on a system and disable software which is n...Group -
Avahi Server
The Avahi daemon implements the DNS Service Discovery and Multicast DNS protocols, which provide service and host discovery on a network. It allows a system to automatically identify resources on t...Group -
Disable Avahi Server if Possible
Because the Avahi daemon service keeps an open network port, it is subject to network attacks. Disabling it can reduce the system's vulnerability to such attacks.Group -
Disable Avahi Server Software
Theavahi-daemon
service can be disabled with the following command:$ sudo systemctl mask --now avahi-daemon.service
Rule Medium Severity -
Application Whitelisting Daemon
Fapolicyd (File Access Policy Daemon) implements application whitelisting to decide file access rights. Applications that are known via a reputation source are allowed access while unknown applicat...Group -
Install fapolicyd Package
Thefapolicyd
package can be installed with the following command:$ sudo yum install fapolicyd
Rule Medium Severity -
Enable the File Access Policy Service
The File Access Policy service should be enabled. Thefapolicyd
service can be enabled with the following command:$ sudo systemctl enable fapolicyd.service
Rule Medium 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 unpredictably on unmanaged systems. Central time protocols can...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 set of servers and having all systems synchronize th...Rule Medium Severity -
The Chronyd service is enabled
chrony is a daemon which implements the Network Time Protocol (NTP) is designed to synchronize system clocks across a variety of systems and use a source that is highly accurate. More information o...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 systems and use a source that is highly accurate. M...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 severely limiting the service has been the best a...Group -
Rlogin, Rsh, and Rexec
The Berkeley r-commands are legacy services which allow cleartext remote access and have an insecure trust model.Group -
Uninstall rsh-server Package
Thersh-server
package can be removed with the following command:$ sudo yum erase rsh-server
Rule High Severity -
Uninstall rsh Package
Thersh
package contains the client commands for the rsh servicesRule Unknown Severity -
Chat/Messaging Services
The talk software makes it possible for users to send and receive messages across systems through a terminal session.Group -
Uninstall talk-server Package
Thetalk-server
package can be removed with the following command:$ sudo yum erase talk-server
Rule Medium Severity -
Uninstall talk Package
The <code>talk</code> package contains the client program for the Internet talk protocol, which allows the user to chat with other users on different systems. Talk is a communication program which ...Rule Medium Severity -
Telnet
The telnet protocol does not provide confidentiality or integrity for information transmitted on the network. This includes authentication information such as passwords. Organizations which use tel...Group -
Uninstall telnet-server Package
Thetelnet-server
package can be removed with the following command:$ sudo yum erase telnet-server
Rule High Severity -
Remove telnet Clients
The telnet client allows users to start connections to other systems via the telnet protocol.Rule Low Severity -
Disable telnet Service
Make sure that the activation of the <code>telnet</code> service on system boot is disabled. The <code>telnet</code> socket can be disabled with the following command: <pre>$ sudo systemctl mask -...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 through it. Therefore, if one is required, the system ac...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 yum erase squid
Rule Unknown Severity -
Disable Squid
Thesquid
service can be disabled with the following command:$ sudo systemctl mask --now squid.service
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 were well-known for weak security, such as plaintex...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 is not needed, the software should be disabled an...Group -
Configure SNMP Server if Necessary
If it is necessary to run the snmpd agent on the system, some best practices should be followed to minimize the security risk from the installation. The multiple security models implemented by SNMP...Group
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