Canonical Ubuntu 20.04 LTS Security Technical Implementation Guide
Rules, Groups, and Values defined within the XCCDF Benchmark
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The Ubuntu operating system must provision temporary user accounts with an expiration time of 72 hours or less.
If temporary user accounts remain active when no longer needed or for an excessive period, these accounts may be used to gain unauthorized access. To mitigate this risk, automated termination of al...Rule Medium Severity -
The Ubuntu operating system must enable the graphical user logon banner to display the Standard Mandatory DoD Notice and Consent Banner before granting local access to the system via a graphical user logon.
Display of a standardized and approved use notification before granting access to the Ubuntu operating system ensures privacy and security notification verbiage used is consistent with applicable f...Rule Medium Severity -
The Ubuntu operating system must retain a user's session lock until that user reestablishes access using established identification and authentication procedures.
A session lock is a temporary action taken when a user stops work and moves away from the immediate physical vicinity of the information system but does not want to log out because of the temporary...Rule Medium Severity -
Ubuntu operating systems when booted must require authentication upon booting into single-user and maintenance modes.
To mitigate the risk of unauthorized access to sensitive information by entities that have been issued certificates by DoD-approved PKIs, all DoD systems (e.g., web servers and web portals) must be...Rule High Severity -
The Ubuntu operating system must automatically terminate a user session after inactivity timeouts have expired.
Automatic session termination addresses the termination of user-initiated logical sessions in contrast to the termination of network connections that are associated with communications sessions (i....Rule Medium Severity -
The Ubuntu operating system must implement smart card logins for multifactor authentication for local and network access to privileged and nonprivileged accounts.
Without the use of multifactor authentication, the ease of access to privileged functions is greatly increased. Multifactor authentication requires using two or more factors to achieve authentica...Rule Medium Severity -
The Ubuntu operating system must immediately terminate all network connections associated with SSH traffic after a period of inactivity.
Automatic session termination addresses the termination of user-initiated logical sessions in contrast to the termination of network connections that are associated with communications sessions (i....Rule Medium Severity -
The Ubuntu operating system must immediately terminate all network connections associated with SSH traffic at the end of the session or after 10 minutes of inactivity.
Terminating an idle session within a short time period reduces the window of opportunity for unauthorized personnel to take control of a management session enabled on the console or console port th...Rule Medium Severity -
The Ubuntu operating system must configure the SSH daemon to use FIPS 140-2 approved ciphers to prevent the unauthorized disclosure of information and/or detect changes to information during transmission.
Without cryptographic integrity protections, information can be altered by unauthorized users without detection. Remote access (e.g., RDP) is access to DOD nonpublic information systems by an aut...Rule Medium Severity -
The Ubuntu operating system must be configured so that remote X connections are disabled, unless to fulfill documented and validated mission requirements.
The security risk of using X11 forwarding is that the client's X11 display server may be exposed to attack when the SSH client requests forwarding. A System Administrator may have a stance in which...Rule High Severity -
The Ubuntu operating system must enforce password complexity by requiring that at least one lower-case character be used.
Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resistin...Rule Low Severity -
The Ubuntu operating system must prevent the use of dictionary words for passwords.
If the Ubuntu operating system allows the user to select passwords based on dictionary words, then this increases the chances of password compromise by increasing the opportunity for successful gue...Rule Medium Severity -
The Ubuntu operating system must be configured so that when passwords are changed or new passwords are established, pwquality must be used.
Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resistin...Rule Medium Severity -
The Ubuntu operating system must implement multifactor authentication for remote access to privileged accounts in such a way that one of the factors is provided by a device separate from the system gaining access.
Using an authentication device, such as a CAC or token that is separate from the information system, ensures that even if the information system is compromised, that compromise will not affect cred...Rule Medium Severity -
The Ubuntu operating system for PKI-based authentication, must implement a local cache of revocation data in case of the inability to access revocation information via the network.
Without configuring a local cache of revocation data, there is the potential to allow access to users who are no longer authorized (users with revoked certificates).Rule Medium Severity -
The Ubuntu operating system must prohibit password reuse for a minimum of five generations.
Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. If the information system or application allows the user...Rule Low Severity -
The Ubuntu operating system must be configured so that the script which runs each 30 days or less to check file integrity is the default one.
Without verification of the security functions, security functions may not operate correctly and the failure may go unnoticed. Security function is defined as the hardware, software, and/or firmwar...Rule Medium Severity -
The Ubuntu operating system must generate audit records for all account creations, modifications, disabling, and termination events that affect /etc/passwd.
Once an attacker establishes access to a system, the attacker often attempts to create a persistent method of reestablishing access. One way to accomplish this is for the attacker to create an acco...Rule Medium Severity -
The Ubuntu operating system must generate audit records for all account creations, modifications, disabling, and termination events that affect /etc/opasswd.
Once an attacker establishes access to a system, the attacker often attempts to create a persistent method of reestablishing access. One way to accomplish this is for the attacker to create an acco...Rule Medium Severity -
The Ubuntu operating system must shut down by default upon audit failure (unless availability is an overriding concern).
It is critical that when the operating system is at risk of failing to process audit logs as required, it takes action to mitigate the failure. Audit processing failures include: software/hardware ...Rule Medium Severity -
The Ubuntu operating system must be configured so that audit configuration files are not write-accessible by unauthorized users.
Without the capability to restrict which roles and individuals can select which events are audited, unauthorized personnel may be able to prevent the auditing of critical events. Misconfigured a...Rule Medium Severity -
The Ubuntu operating system must generate audit records for successful/unsuccessful uses of the umount command.
Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an in...Rule Medium Severity -
The Ubuntu operating system must generate audit records for any use of the setxattr, fsetxattr, lsetxattr, removexattr, fremovexattr, and lremovexattr system calls.
Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an in...Rule Medium Severity -
The Ubuntu operating system must generate audit records for successful/unsuccessful uses of the chmod, fchmod, and fchmodat system calls.
Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an in...Rule Medium Severity -
The Ubuntu operating system must generate audit records for successful/unsuccessful uses of the newgrp command.
Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an in...Rule Medium Severity -
The Ubuntu operating system must generate audit records for the use and modification of faillog file.
Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an in...Rule Medium Severity -
The Ubuntu operating system must generate audit records for successful/unsuccessful uses of the crontab command.
Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an in...Rule Medium Severity -
The Ubuntu operating system must generate audit records for successful/unsuccessful uses of the init_module and finit_module syscalls.
Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an in...Rule Medium Severity -
The Ubuntu operating system must configure audit tools with a mode of 0755 or less permissive.
Protecting audit information also includes identifying and protecting the tools used to view and manipulate log data. Therefore, protecting audit tools is necessary to prevent unauthorized operatio...Rule Medium Severity -
The Ubuntu operating system must configure the audit tools to be group-owned by root.
Protecting audit information also includes identifying and protecting the tools used to view and manipulate log data. Therefore, protecting audit tools is necessary to prevent unauthorized operatio...Rule Medium Severity -
The Ubuntu operating system must prevent all software from executing at higher privilege levels than users executing the software and the audit system must be configured to audit the execution of privileged functions.
In certain situations, software applications/programs need to execute with elevated privileges to perform required functions. However, if the privileges required for execution are at a higher level...Rule Medium Severity -
The Ubuntu operating system must generate audit records for privileged activities, nonlocal maintenance, diagnostic sessions and other system-level access.
If events associated with nonlocal administrative access or diagnostic sessions are not logged, a major tool for assessing and investigating attacks would not be available. This requirement addr...Rule Medium Severity -
The Ubuntu operating system must generate audit records when successful/unsuccessful attempts to use the kmod command.
Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an in...Rule Medium Severity -
The Ubuntu operating system must limit the number of concurrent sessions to ten for all accounts and/or account types.
The Ubuntu operating system management includes the ability to control the number of users and user sessions that utilize an operating system. Limiting the number of allowed users and sessions per ...Rule Low Severity -
The Ubuntu operating system must encrypt all stored passwords with a FIPS 140-2 approved cryptographic hashing algorithm.
Passwords need to be protected at all times, and encryption is the standard method for protecting passwords. If passwords are not encrypted, they can be plainly read (i.e., clear text) and easily c...Rule Medium Severity -
The Ubuntu operating system must not have the rsh-server package installed.
It is detrimental for operating systems to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities or services are often overlooke...Rule High Severity -
The Ubuntu operating system must prevent direct login into the root account.
To assure individual accountability and prevent unauthorized access, organizational users must be individually identified and authenticated. A group authenticator is a generic account used by mu...Rule Medium Severity -
The Ubuntu operating system must automatically expire temporary accounts within 72 hours.
Temporary accounts are privileged or nonprivileged accounts that are established during pressing circumstances, such as new software or hardware configuration or an incident response, where the nee...Rule Low Severity -
Ubuntu operating systems handling data requiring "data at rest" protections must employ cryptographic mechanisms to prevent unauthorized disclosure and modification of the information at rest.
Information at rest refers to the state of information when it is located on a secondary storage device (e.g., disk drive and tape drive, when used for backups) within an operating system. This ...Rule Medium Severity -
The Ubuntu operating system must configure the /var/log directory to be owned by root.
Only authorized personnel should be aware of errors and the details of the errors. Error messages are an indicator of an organization's operational state or can identify the operating system or pla...Rule Medium Severity -
The Ubuntu operating system must configure the /var/log directory to have mode "0755" or less permissive.
Only authorized personnel should be aware of errors and the details of the errors. Error messages are an indicator of an organization's operational state or can identify the operating system or pla...Rule Medium Severity -
The Ubuntu operating system must have directories that contain system commands set to a mode of 0755 or less permissive.
Protecting audit information also includes identifying and protecting the tools used to view and manipulate log data. Therefore, protecting audit tools is necessary to prevent unauthorized operatio...Rule Medium Severity -
The Ubuntu operating system must have directories that contain system commands group-owned by root.
Protecting audit information also includes identifying and protecting the tools used to view and manipulate log data. Therefore, protecting audit tools is necessary to prevent unauthorized operatio...Rule Medium Severity -
The Ubuntu operating system library directories must have mode 0755 or less permissive.
If the operating system were to allow any user to make changes to software libraries, then those changes might be implemented without undergoing the appropriate testing and approvals that are part...Rule Medium Severity -
The Ubuntu operating system library directories must be owned by root.
If the operating system were to allow any user to make changes to software libraries, then those changes might be implemented without undergoing the appropriate testing and approvals that are part...Rule Medium Severity -
The Ubuntu operating system must have an application firewall installed in order to control remote access methods.
Remote access services, such as those providing remote access to network devices and information systems, which lack automated control capabilities, increase risk and make remote user access manage...Rule Medium Severity -
The Ubuntu operating system must enable and run the uncomplicated firewall(ufw).
Remote access services, such as those providing remote access to network devices and information systems, which lack automated control capabilities, increase risk and make remote user access manage...Rule Medium Severity -
The Ubuntu operating system must be configured to use AppArmor.
Control of program execution is a mechanism used to prevent execution of unauthorized programs. Some operating systems may provide a capability that runs counter to the mission or provides users wi...Rule Medium Severity -
The Ubuntu operating system must implement NIST FIPS-validated cryptography to protect classified information and for the following: To provision digital signatures, to generate cryptographic hashes, and to protect unclassified information requiring confidentiality and cryptographic protection in accordance with applicable federal laws, Executive Orders, directives, policies, regulations, and standards.
Use of weak or untested encryption algorithms undermines the purposes of utilizing encryption to protect data. The operating system must implement cryptographic modules adhering to the higher stand...Rule High Severity -
The Ubuntu operating system must implement nonexecutable data to protect its memory from unauthorized code execution.
Some adversaries launch attacks with the intent of executing code in nonexecutable regions of memory or in memory locations that are prohibited. Security safeguards employed to protect memory inclu...Rule Medium Severity
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