| V-271920 | high | The Cisco ACI must be configured to prohibit the use of all unnecessary and/or nonsecure functions, ports, protocols, and/or services. | To prevent unauthorized connection of devices, unauthorized transfer of information, or unauthorized tunneling (i.e., embedding of data types within data types), organizations must disable unused or unnecessary physical and logical ports/protocols on information systems.
By default, Cisco ACI only exposes two ports from the outside:
- HTTPS (TCP 443) for GUI access and REST API access, on both the APIC and switches.
- SSH (TCP 22) for CLI access, on both the APIC and switches.
Cisco ACI enables Link Layer Discovery Protocol (LLDP) by default to support zero-touch fabric provisioning. DOD sites may keep LLDP enabled on trusted interfaces for loop prevention and VMM integration. Sites must disable LLDP on interfaces facing untrusted networks.
Cisco ACI is designed not to run nonrequired services by default, as well as to limit remote management services or protocols that are active by default. Hence, there is no action required from an administrator standpoint to disable them. If any other protocol is required, such as SNMP, administrators must explicitly configure it. |
| V-271924 | high | The Cisco Application Policy Infrastructure Controller (APIC) must be configured to use at least two authentication servers for the purpose of authenticating users prior to granting administrative access. | Centralized management of authentication settings increases the security of remote and nonlocal access methods. This control is particularly important protection against the insider threat. With robust centralized management, audit records for administrator account access to the organization's Cisco ACIs can be more readily analyzed for trends and anomalies. The alternative method of defining administrator accounts on each device exposes the device configuration to remote access authentication attacks and system administrators with multiple authenticators for each Cisco ACI.
APIC policies manage the authentication, authorization, and accounting (AAA) functions of the Cisco ACI fabric. The combination of user privileges, roles, and domains with access rights inheritance enables administrators to configure AAA functions at the managed object level in a granular fashion. Creating a user and assigning a role to that user does not enable access rights. It is necessary to also assign the user to one or more security domains. By default, the ACI fabric includes two special precreated domains:
- "All" allows access to the entire MIT.
- "Infra" allows access to fabric infrastructure objects/subtrees, such as fabric access policies.
Satisfies: SRG-APP-000149-NDM-000247, SRG-APP-000001-NDM-000200 |
| V-271926 | high | The Cisco ACI must be running an operating system release that is currently supported by the vendor. | Cisco ACIs running an unsupported operating system lack current security fixes required to mitigate the risks associated with recent vulnerabilities. |
| V-271927 | high | The Cisco ACI must be configured to assign appropriate user roles or access levels to authenticated users. | Successful identification and authentication must not automatically give an entity full access to a Cisco ACI or security domain. The lack of authorization-based access control could result in the immediate compromise of, and unauthorized access to, sensitive information. All DOD systems must be properly configured to incorporate access control methods that do not rely solely on authentication for authorized access.
Security domains allow fabric administrators to expose resources selectively to a set of users and provide those users with the required level of permissions to read and modify those resources. By using security domains, multiple sets of users can share the underlying infrastructure while having separated management access to their resources.
Although out of scope for this STIG, the authentication server will also need to be configured with the security groups or access levels available on the Cisco ACIs and convey that information to the AAA operator of the Cisco ACI. Once the AAA broker identifies the user persona on the centralized directory service, the user's security group memberships can be retrieved. The AAA operator will then create a mapping that links target security groups from the directory service to the appropriate security groups or access levels on the Cisco ACI. Once these mappings are configured, authorizations can happen dynamically, based on each user's directory service group membership.
Satisfies: SRG-APP-000033-NDM-000212, SRG-APP-000329-NDM-000287, SRG-APP-000177-NDM-000263, SRG-APP-000910-NDM-000300 |
| V-271931 | high | The Cisco ACI must be configured to send log data to a central log server for log retention and forwarding alerts to the administrators and the information system security officer (ISSO). | The aggregation of log data kept on a syslog server can be used to detect attacks and trigger an alert to the appropriate security personnel. The stored log data can be used to detect weaknesses in security that enable the network IA team to find and address these weaknesses before breaches can occur. Reviewing these logs, whether before or after a security breach, is important in determining whether someone is an internal employee or an outside threat. |
| V-271966 | high | The Cisco ACI must use FIPS 140-2/140-3 approved algorithms for authentication to a cryptographic module. | Unapproved mechanisms used for authentication to the cryptographic module are not validated and therefore, cannot be relied on to provide confidentiality or integrity, and DOD data may be compromised.
Cisco ACIs using encryption are required to use FIPS-compliant mechanisms for authenticating to cryptographic modules.
FIPS 140-2/140-3 is the current standard for validating that mechanisms used to access cryptographic modules use authentication that meets DOD requirements. However, authentication algorithms must configure security processes to use only FIPS-approved and NIST-recommended authentication algorithms.
Satisfies: SRG-APP-000179-NDM-000265, SRG-APP-000411-NDM-000330, SRG-APP-000412-NDM-000331 |
| V-271969 | high | Cisco ACI SSH sessions must be terminated after five 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 that has been left unattended. Quickly terminating an idle session will also free up resources committed by the managed network element.
Terminating network connections associated with communications sessions includes, for example, deallocating associated TCP/IP address/port pairs at the operating system level or deallocating networking assignments at the application level if multiple application sessions are using a single, operating system-level network connection. This does not mean that the device terminates all sessions or network access; it only ends the inactive session and releases the resources associated with that session. |
| V-271916 | medium | The Cisco ACI must record time stamps for audit records that can be mapped to Coordinated Universal Time (UTC). | If time stamps are not consistently applied and there is no common time reference, it is difficult to perform forensic analysis.
Time stamps generated by the application include date and time. Time is commonly expressed in UTC or local time with an offset from UTC. |
| V-271917 | medium | The Cisco ACI must be configured to authenticate SNMP messages using a FIPS-validated Keyed-Hash Message Authentication Code (HMAC). | Without authenticating devices, unidentified or unknown devices may be introduced, thereby facilitating malicious activity. Bidirectional authentication provides stronger safeguards to validate the identity of other devices for connections that are of greater risk.
A local connection is any connection with a device communicating without the use of a network. A network connection is any connection with a device that communicates through a network (e.g., local area or wide area network, internet). A remote connection is any connection with a device communicating through an external network (e.g., the internet).
Because of the challenges of applying this requirement on a large scale, organizations are encouraged to only apply the requirement to those limited number (and type) of devices that truly need to support this capability. |
| V-271918 | medium | The Cisco ACI must display the Standard Mandatory DOD Notice and Consent Banner before granting access to the device. | Display of the DOD-approved use notification before granting access to the Cisco ACI ensures privacy and security notification verbiage used is consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance.
System use notifications are required only for access via logon interfaces with human users. |
| V-271919 | medium | The Cisco ACI must be configured to enforce the limit of three consecutive invalid logon attempts, after which time it must block any login attempt for 15 minutes. | By limiting the number of failed login attempts, the risk of unauthorized system access via user password guessing, otherwise known as brute-forcing, is reduced.
For Cisco ACI, when a user is in a locked-out state, the lockout is enforced in all nodes that are part of the fabric, including controllers and switches. |
| V-271921 | medium | The Cisco ACI must conduct backups of the configuration weekly or at an organization-defined frequency and store on a separate device. | Information system backup is a critical step in maintaining data assurance and availability. Information system and security-related documentation contains information pertaining to system configuration and security settings. If this information were not backed up, and a system failure were to occur, the security settings would be difficult to reconfigure quickly and accurately. Maintaining a backup of information system and security-related documentation provides for a quicker recovery time when system outages occur. This control requires the Cisco ACI to support the organizational central backup process for user account information associated with the Cisco ACI. This function may be provided by the Cisco ACI itself; however, the preferred best practice is a centralized backup rather than each Cisco ACI performing discrete backups.
With ACI, all components of the ACI Fabric are treated as one entity (leaves, spines, APIC controllers). The ACI Fabric configuration, while made up of different managed objects, is combined into one tar/gz zipfile, which greatly improves the configuration backup process, as well as the configuration restoration process. Finally, the backups can be configured as one-time backup jobs, or they can be scheduled in a daily or weekly scheduler to export the entire Fabric configuration to a remote location (i.e., external server) using SCP, FTP, or SFTP. Cisco ACI allows administrators to perform on-demand and periodic snapshots. Those snapshots can be saved either locally or in a remote location. Cisco ACI configuration contains many sensitive details, including passwords and secrets. Therefore, backup configuration must be properly secured and stored in a secure remote location, ensuring that sensitive information on the configuration files is not disclosed. Set the AES passphrase immediately after fabric bring-up and store the passphrase in a safe location external to the APIC. This passphrase must be provided by the administrator to unencrypt the configuration backup needed to restore the fabric should a disaster happen. |
| V-271922 | medium | The Cisco ACI must obtain its public key certificates from an appropriate certificate policy through an approved service provider. | After the Cisco ACI is initialized, it uses the self-signed certificate as the SSL certificate for HTTPS. This self-signed certificate is neither appropriate nor approved for use in DOD. |
| V-271923 | medium | The Cisco ACI must use DOD-approved Network Time Protocol (NTP) sources that use authentication that is cryptographically based. | If NTP is not authenticated, an attacker can introduce a rogue NTP server. This rogue server can then be used to send incorrect time information to Cisco ACIs, which will make log timestamps inaccurate and affect scheduled actions. NTP authentication is used to prevent this tampering by authenticating the time source.
Time synchronization plays a critical role in the ACI fabric. From validating certificates, to keeping log files across devices consistent, it is strongly encouraged to sync the ACI fabric to redundant time sources. Simply creating an NTP policy does not apply it to the fabric. This policy will need to be updated to a "Pod Policy".
Do not enable the NTP server option that allows the leaf switches to serve time requests to downstream endpoints. Using a Bridge Domain SVI (Subnet IP) as an NTP Source for downstream clients is not recommended. When a leaf switch is enabled as NTP server, it will respond on any interface. Issues can arise when attempting to use the SVI address of a leaf, rather than the management IP. |
| V-271929 | medium | The Cisco ACI must be configured with only one local account to be used as the account of last resort in the event the authentication server is unavailable. | Authentication for administrative (privileged level) access to the device is required at all times. An account can be created on the device's local database for use when the authentication server is down or connectivity between the device and the authentication server is not operable. This account is referred to as the account of last resort since it is intended to be used as a last resort and when immediate administrative access is absolutely necessary.
In the initial configuration script for the Cisco ACI, the admin account is configured and the admin is the only user when the system starts.
The account of last resort logon credentials must be stored in a sealed envelope and kept in a safe. The safe must be periodically audited to verify the envelope remains sealed. The signature of the auditor and the date of the audit should be added to the envelope as a record. Administrators should secure the credentials and disable the root account (if possible) when not needed for system administration functions. |
| V-271932 | medium | The Cisco ACI must be configured to alert organization-defined personnel or roles upon detection of unauthorized access, modification, or deletion of audit information. | Audit information includes all information needed to successfully audit system activity, such as audit records, audit log settings, audit reports, and personally identifiable information. Audit logging tools are those programs and devices used to conduct system audit and logging activities. Protection of audit information focuses on technical protection and limits the ability to access and execute audit logging tools to authorized individuals. Physical protection of audit information is addressed by both media protection controls and physical and environmental protection controls. |
| V-271933 | medium | The Cisco ACI must audit the enforcement actions used to restrict access associated with changes to the device. | Without auditing the enforcement of access restrictions against changes to the device configuration, it will be difficult to identify attempted attacks, and an audit trail will not be available for forensic investigation for after-the-fact actions.
Enforcement actions are the methods or mechanisms used to prevent unauthorized changes to configuration settings. Enforcement action methods may be as simple as denying access to a file based on the application of file permissions (access restriction). Audit items may consist of lists of actions blocked by access restrictions or changes identified after the fact.
Satisfies: SRG-APP-000381-NDM-000305, SRG-APP-000080-NDM-000220 |
| V-271935 | medium | The Cisco ACI must allocate audit record storage capacity in accordance with organization-defined audit record storage requirements. | To ensure Cisco ACIs have a sufficient storage capacity in which to write the audit logs, they need to be able to allocate audit record storage capacity. The task of allocating audit record storage capacity is usually performed during initial device setup if it is modifiable.
The value for the organization-defined audit record storage requirement will depend on the amount of storage available on the Cisco ACI, the anticipated volume of logs, the frequency of transfer from the Cisco ACI to centralized log servers, and other factors. |
| V-271936 | medium | The Cisco ACI must implement replay-resistant authentication mechanisms for network access to privileged accounts. | A replay attack may enable an unauthorized user to gain access to the application. authentication sessions between the authenticator and the application validating the user credentials must not be vulnerable to a replay attack.
An authentication process resists replay attacks if it is impractical to achieve a successful authentication by recording and replaying a previous authentication message.
Techniques used to address this include protocols using nonces (e.g., numbers generated for a specific one-time use) or challenges (e.g., TLS, WS_Security). Additional techniques include time-synchronous or challenge-response one-time authenticators. |
| V-271939 | medium | The Cisco ACI must automatically audit account creation. | Upon gaining access to a Cisco ACI, an attacker will often first attempt to create a persistent method of reestablishing access. One way to accomplish this is to create a new account. Notification of account creation helps to mitigate this risk. Auditing account creation provides the necessary reconciliation that account management procedures are being followed. Without this audit trail, personnel without the proper authorization may gain access to critical network nodes.
System messages are created by various sources, such as the Application Policy Infrastructure Controller (APIC) or the spine and leaf switches in the ACI fabric. System messages from the switches can be generated by either of the following processes: the underlying NX-OS operating system of the spine and leaf switches or the ACI-related processes in the switch. This requirement sets the default logging level on the ACI to 7. This information severity level captures normal but significant condition messages and is the level required.
Satisfies: SRG-APP-000026-NDM-000208, SRG-APP-000027-NDM-000209, SRG-APP-000028-NDM-000210, SRG-APP-000029-NDM-000211, SRG-APP-000343-NDM-00028, SRG-APP-000091-NDM-000223, SRG-APP-000091-NDM-000223, SRG-APP-000495-NDM-000318, SRG-APP-000499-NDM-000319, SRG-APP-000503-NDM-000320, SRG-APP-000503-NDM-000320, SRG-APP-000504-NDM-000321, SRG-APP-000101-NDM-000231, SRG-APP-000095-NDM-000225, SRG-APP-000096-NDM-000226, SRG-APP-000097-NDM-000227, SRG-APP-000098-NDM-000228, SRG-APP-000099-NDM-000229, SRG-APP-000100-NDM-000230 |
| V-271944 | medium | The Cisco ACI must generate log records for a locally developed list of auditable events. | Auditing and logging are key components of any security architecture. Logging the actions of specific events provides a means to investigate an attack; to recognize resource utilization or capacity thresholds; or to identify an improperly configured Cisco ACI. If auditing is not comprehensive, it will not be useful for intrusion monitoring, security investigations, and forensic analysis. |
| V-271958 | medium | The Cisco ACI must be configured to allow user selection of long passwords and passphrases, including spaces and all printable characters, for password-based authentication. | Password-based authentication applies to passwords regardless of whether they are used in single-factor or multifactor authentication. Long passwords or passphrases are preferable over shorter passwords. Enforced composition rules provide marginal security benefits while decreasing usability. However, organizations may choose to establish certain rules for password generation (e.g., minimum character length for long passwords) under certain circumstances and can enforce this requirement in IA-5(1)(h). Account recovery can occur, for example, in situations when a password is forgotten. Cryptographically protected passwords include salted one-way cryptographic hashes of passwords. The list of commonly used, compromised, or expected passwords includes passwords obtained from previous breach corpuses, dictionary words, and repetitive or sequential characters. The list includes context-specific words, such as the name of the service, username, and derivatives thereof.
Satisfies: SRG-APP-000860-NDM-000250, SRG-APP-000865-NDM-000260, SRG-APP-000167-NDM-000255, SRG-APP-000168-NDM-000256, SRG-APP-000169-NDM-000257 |
| V-271960 | medium | The Cisco ACI must enforce a minimum 15-character password length. | Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. Password length is one factor of several that helps to determine strength and how long it takes to crack a password.
The shorter the password, the lower the number of possible combinations that must be tested before the password is compromised. Use of more characters in a password helps to increase exponentially the time and/or resources required to compromise the password. |
| V-271971 | medium | The Cisco ACI must be configured to synchronize system clocks within and between systems or system components. | Time synchronization of system clocks is essential for the correct execution of many system services, including identification and authentication processes that involve certificates and time-of-day restrictions as part of access control. Denial of service or failure to deny expired credentials may result without properly synchronized clocks within and between systems and system components. Time is commonly expressed in Coordinated Universal Time (UTC), a modern continuation of Greenwich Mean Time (GMT), or local time with an offset from UTC. The granularity of time measurements refers to the degree of synchronization between system clocks and reference clocks, such as clocks synchronizing within hundreds of milliseconds or tens of milliseconds. Organizations may define different time granularities for system components. Time service can be critical to other security capabilities such as access control and identification and authentication depending on the nature of the mechanisms used to support the capabilities. |
| V-271972 | medium | The Cisco ACI must be configured to disable the auxiliary USB port. | Disable the USB port in those environments where physical access to the devices is not strictly controlled, or in environments where this extra layer of protection is required.
Cisco Nexus 9000 switches running Cisco ACI code have the USB port enabled by default. When the USB port is enabled, switches will try to boot from the USB drive first. This may be a security risk in case a malicious actor has physical access to the switch, given they could power-cycle the device to try to boot the switch from a USB image that contains malicious code.
Even if this is not a common scenario considering that most organizations have physical access security guidelines in place, Cisco ACI release 5.2(3) introduced the option to disable the USB port using a specific switch policy. |
| V-271975 | medium | The Cisco ACI must limit the number of concurrent sessions to one for each administrator account. | Device management includes the ability to control the number of administrators and management sessions that manage a device. Limiting the number of allowed administrators and sessions per administrator based on account type, role, or access type is helpful in limiting risks related to denial-of-service (DoS) attacks.
This requirement addresses concurrent sessions for administrative accounts and does not address concurrent sessions by a single administrator via multiple administrative accounts. The maximum number of concurrent sessions should be defined based upon mission needs and the operational environment for each system. At a minimum, limits must be set for SSH, HTTPS, account of last resort, and root account sessions. |