HYCU for Nutanix Security Technical Implementation Guide

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 DoS attacks.

A session lock is a temporary network device or administrator-initiated action taken when the administrator stops work but does not log out of the network device. Rather than relying on the user to manually lock their management session prior to vacating the vicinity, network devices need to be able to identify when a management session has idled and take action to initiate the session lock. Once invoked, the session lock must remain in place until the administrator reauthenticates. No other system activity aside from reauthentication must unlock the management session.

A shared/group account credential is a shared form of authentication that allows multiple individuals to access the network device using a single account. If shared/group account credentials are not terminated when individuals leave the group, the user that left the group can still gain access even though they are no longer authorized. There may also be instances when specific user actions need to be performed on the network device without unique administrator identification or authentication. Examples of credentials include passwords and group membership certificates.

Discretionary Access Control (DAC) is based on the notion that individual network administrators are "owners" of objects and therefore have discretion over who should be authorized to access the object and in which mode (e.g., read or write). Ownership is usually acquired as a consequence of creating the object or via specified ownership assignment. DAC allows the owner to determine who will have access to objects they control. An example of DAC includes user-controlled file permissions. Satisfies: SRG-APP-000328-NDM-000286, SRG-APP-000329-NDM-000287

A mechanism to detect and prevent unauthorized communication flow must be configured or provided as part of the system design. If management information flow is not enforced based on approved authorizations, the network device may become compromised. Information flow control regulates where management information is allowed to travel within a network device. The flow of all management information must be monitored and controlled so it does not introduce any unacceptable risk to the network device or data.

Misuse of privileged functions, either intentionally or unintentionally by authorized users, or by unauthorized external entities that have compromised information system accounts, is a serious and ongoing concern and can have significant adverse impacts on organizations. Auditing the use of privileged functions is one way to detect such misuse and identify the risk from insider threats and the advanced persistent threat.

By limiting the number of failed logon attempts, the risk of unauthorized system access via user password guessing, otherwise known as brute-forcing, is reduced.

Display of the DoD-approved use notification before granting access to the network device ensures privacy and security notification verbiage used is consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance.

The banner must be acknowledged by the administrator prior to the device allowing the administrator access to the network device. This provides assurance that the administrator has seen the message and accepted the conditions for access. If the consent banner is not acknowledged by the administrator, DoD will not comply with system use notifications required by law.

It is detrimental for applications to provide functionality exceeding requirements or mission objectives. These unnecessary capabilities or services are often overlooked and therefore may remain unsecured. They increase the risk to the platform by providing additional attack vectors. Examples of non-essential capabilities include but are not limited to software packages, tools, and demonstration software not related to requirements or providing a wide array of functionality not required for every mission but that cannot be disabled. Remote access using SSH is not required for administration as all administrative tasks can be performed either through the web interface or local console. SSH must be disabled to limit exposure.

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 incident or identify those responsible for one. Audit records can be generated from various components within the information system (e.g., module or policy filter).

This requirement addresses the configuration of network devices to mitigate the impact of DoS attacks that have occurred or are ongoing on device availability. For each network device, known and potential DoS attacks must be identified and solutions for each type implemented. A variety of technologies exist to limit or, in some cases, eliminate the effects of DoS attacks (e.g., limiting processes or restricting the number of sessions the device opens at one time). Employing increased capacity and bandwidth, combined with service redundancy, may reduce the susceptibility to some DoS attacks. Satisfies: SRG-APP-000495-NDM-000318, SRG-APP-000499-NDM-000319

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 incident or identify those responsible for one.

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 incident or identify those responsible for one. Audit records can be generated from various components within the network device (e.g., module or policy filter). Satisfies: SRG-APP-000504-NDM-000321, SRG-APP-000506-NDM-000323, SRG-APP-000516-NDM-000334

It is essential for security personnel to know what is being done, what was attempted, where it was done, when it was done, and by whom it was done in order to compile an accurate risk assessment. Logging the date and time of each detected event provides a means of investigating an attack; recognizing resource utilization or capacity thresholds; or identifying an improperly configured network device. In order to establish and correlate the series of events leading up to an outage or attack, it is imperative the date and time are recorded in all log records. In order to compile an accurate risk assessment and provide forensic analysis, it is essential for security personnel to know where events occurred, such as device hardware components, device software modules, session identifiers, filenames, host names, and functionality. In order to compile an accurate risk assessment and provide forensic analysis, it is essential for security personnel to know the source of the event. The source may be a component, module, or process within the device or an external session, administrator, or device. Without information about the outcome of events, security personnel cannot make an accurate assessment as to whether an attack was successful or if changes were made to the security state of the system. Event outcomes can include indicators of event success or failure and event-specific results (e.g., the security state of the device after the event occurred). As such, they also provide a means to measure the impact of an event and help authorized personnel to determine the appropriate response. Satisfies: 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

Without information that establishes the identity of the subjects (i.e., administrators or processes acting on behalf of administrators) associated with the events, security personnel cannot determine responsibility for the potentially harmful event. Event identifiers (if authenticated or otherwise known) include, but are not limited to, user database tables, primary key values, user names, or process identifiers.

Reconstruction of harmful events or forensic analysis is not possible if audit records do not contain enough information. Organizations consider limiting the additional audit information to only that information explicitly needed for specific audit requirements. The additional information required is dependent on the type of information (i.e., sensitivity of the data and the environment within which it resides). At a minimum, the organization must audit full-text recording of privileged commands. The organization must maintain audit trails in sufficient detail to reconstruct events to determine the cause and impact of compromise.

It is essential for security personnel to know what is being done, what was attempted, where it was done, when it was done, and by whom it was done in order to compile an accurate risk assessment. Associating event types with detected events in the application and audit logs provides a means of investigating an attack; recognizing resource utilization or capacity thresholds; or identifying an improperly configured network device. Without this capability, it would be difficult to establish, correlate, and investigate the events leading up to an outage or attack. If auditing is enabled late in the startup process, the actions of some start-up processes may not be audited. Some audit systems also maintain state information only available if auditing is enabled before a given process is created. Satisfies: SRG-APP-000095-NDM-000225, SRG-APP-000319-NDM-000283, SRG-APP-000353-NDM-000292, SRG-APP-000495-NDM-000318, SRG-APP-000499-NDM-000319, SRG-APP-000503-NDM-000320, SRG-APP-000504-NDM-000321, SRG-APP-000505-NDM-000322, SRG-APP-000092-NDM-000224

To ensure network devices have a sufficient storage capacity in which to write the audit logs, they must 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 can be modified.

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. System-level information includes default and customized settings and security attributes, including ACLs that relate to the network device configuration, as well as software required for the execution and operation of the device. Information system backup is a critical step in ensuring system integrity and availability. If the system fails and there is no backup of the system-level information, a denial-of-service condition is possible for all who use this critical network component. Information stored in one location is vulnerable to accidental or incidental deletion or alteration. Offloading is a common process in information systems with limited audit storage capacity. Satisfies: SRG-APP-000515-NDM-000325, SRG-APP-000516-NDM-000340, SRG-APP-000516-NDM-000341

It is critical for the appropriate personnel to be aware if a system is at risk of failing to process audit logs as required. Without a real-time alert, security personnel may be unaware of an impending failure of the audit capability and system operation may be adversely affected.

The loss of connectivity to a particular authoritative time source will result in the loss of time synchronization (free-run mode) and increasingly inaccurate time stamps on audit events and other functions.

Audit information includes all information (e.g., audit records, audit settings, and audit reports) needed to successfully audit information system activity. If audit data were to become compromised, then forensic analysis and discovery of the true source of potentially malicious system activity is impossible to achieve. To ensure the veracity of audit data, the network device must protect audit information from unauthorized deletion. This requirement can be achieved through multiple methods, which will depend upon system architecture and design. Some commonly employed methods include: ensuring log files receive the proper file system permissions utilizing file system protections, restricting access, and backing up log data to ensure log data is retained. Network devices providing a user interface to audit data will leverage user permissions and roles identifying the user accessing the data and the corresponding rights the user enjoys in order to make access decisions regarding the deletion of audit data.

Protecting audit data also includes identifying and protecting the tools used to view and manipulate log data. Therefore, protecting audit tools is necessary to prevent unauthorized operation on audit data. Network devices providing tools to interface with audit data will leverage user permissions and roles identifying the user accessing the tools and the corresponding rights the user enjoys in order to make access decisions regarding the access to audit tools. Audit tools include, but are not limited to, vendor-provided and open source audit tools needed to successfully view and manipulate audit information system activity and records. Audit tools include custom queries and report generators. Satisfies: SRG-APP-000121-NDM-000238, SRG-APP-000122-NDM-000239, SRG-APP-000123-NDM-000240

Protection of log data includes assuring log data is not accidentally lost or deleted. Regularly backing up audit records to a different system or onto separate media than the system being audited helps to assure, in the event of a catastrophic system failure, the audit records will be retained.

For user certificates, each organization obtains certificates from an approved, shared service provider, as required by OMB policy. For federal agencies operating a legacy public key infrastructure cross-certified with the Federal Bridge Certification Authority at medium assurance or higher, this Certification Authority will suffice.

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.

If Network Time Protocol is not authenticated, an attacker can introduce a rogue NTP server. This rogue server can then be used to send incorrect time information to network devices, which will make log timestamps inaccurate and affect scheduled actions. NTP authentication is used to prevent this tampering by authenticating the time source.

Use of a complex passwords 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 resisting attempts at guessing and brute-force attacks. Password complexity is one factor of several that determine how long it takes to crack a password. The more complex the password is, the greater the number of possible combinations that need to be tested before the password is compromised. Multifactor authentication (MFA) is required for all administrative and user accounts on network devices, except for an account of last resort and (where applicable) a root account. Passwords should only be used when MFA using PKI is not available, and for the account of last resort and root account. Satisfies: SRG-APP-000166-NDM-000254, SRG-APP-000167-NDM-000255, SRG-APP-000168-NDM-000256, SRG-APP-000169-NDM-000257

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 need to be tested before the password is compromised. Use of more characters in a password helps to exponentially increase the time and/or resources required to compromise the password. Satisfies: SRG-APP-000164-NDM-000252, SRG-APP-000343-NDM-000289

If the application allows the user to consecutively reuse extensive portions of passwords, this increases the chances of password compromise by increasing the window of opportunity for attempts at guessing and brute-force attacks. The number of changed characters refers to the number of changes required with respect to the total number of positions in the current password. In other words, characters may be the same within the two passwords; however, the positions of the like characters must be different. Multifactor authentication (MFA) is required for all administrative and user accounts on network devices, except for an account of last resort and (where applicable) a root account. Passwords should only be used when MFA using PKI is not available, and for the account of last resort and root account.

Virtual Machines not protected with strong password schemes provide the opportunity for anyone to crack the password and gain access to the device, which can result in loss of availability, confidentiality, or integrity of network traffic. Many default vendor passwords are well known or are easily guessed; therefore, not removing them prior to deploying the network device into production provides an opportunity for a malicious user to gain unauthorized access to the device.

Some authentication implementations can be configured to use cached authenticators. If cached authentication information is out-of-date, the validity of the authentication information may be questionable. The organization-defined time period should be established for each device depending on the nature of the device; for example, a device with just a few administrators in a facility with spotty network connectivity may merit a longer caching time period than a device with many administrators.

Sequentially generated session IDs can be easily guessed by an attacker. Employing the concept of randomness in the generation of unique session identifiers helps to protect against brute-force attacks to determine future session identifiers. Unique session IDs address man-in-the-middle attacks, including session hijacking or insertion of false information into a session. If the attacker is unable to identify or guess the session information related to pending application traffic, they will have more difficulty in hijacking the session or otherwise manipulating valid sessions. This requirement is applicable to devices that use a web interface for device management.