Forescout Network Access Control Security Technical Implementation Guide

Connections that bypass established security controls should be allowed only in cases of administrative need. These procedures and use cases must be approved by the Information System Security Manager (ISSM). This setting may be sent from the assessment server, a central server, or from the remediation server. Verify the user is notified and accepts (e.g., using an accept button) that remediation is needed and is about to begin.

Requiring authentication and authorization of both the user's identity and the identity of the computing device is essential to ensuring a non-authorized person or device has entered the network.

Notifications sent to the user and/or network administrator informing them of remediation requirements will ensure that action is taken.

Devices not compliant with DoD secure configuration policies are vulnerable to attack. Allowing these systems to connect presents a danger to the enclave. Verify that Forescout is not allowed to communicate with other hosts in the DMZ that do not perform security policy assessment or remediation services.

Ensuring the conditions that are configured in policy have proper time limits set to reflect changes will allow for proper access. This will help to validate that authorized individuals have proper access.

This requirement gives the option to configure for automated remediation and/or manual remediation. A detailed record must be passed to the remediation server for action. Alternatively, the details can be passed in a notice to the user for action. The device status will be updated on the network access server/authentication server so that further access attempts are denied. The NAC must have policy assessment mechanisms with granular control to distinguish between access restrictions based on the criticality of the software or setting failure.

Devices that do not meet minimum-security configuration requirements pose a risk to the DoD network and information assets. Endpoint devices must be disconnected or given limited access as designated by the approval authority and system owner if the device fails the authentication or security assessment. The user will be presented with a limited portal, which does not include access options for sensitive resources. Required security checks must implement DoD policy requirements.

Keeping an established, connection-oriented audit record is essential to keeping audit logs in accordance with DoD requirements.

Having a separate, secure location for log records is essential to the preservation of logs as required by policy.

Ensuring that a security solution alerts in the event of misconfiguration or error is imperative to ensuring that proper auditing is being conducted. Having the ability to immediately notify an administrator when this auditing fails allows for a quick response and real-time remediation.

Authenticating all devices as they connect to the network is the baseline of a good security solution. This is especially important prior to posture assessment to ensure authorized devices are online and have the proper posture prior to accessing the production network. Device authentication is a solution enabling an organization to manage devices. It is an additional layer of authentication ensuring that only specific preauthorized devices can access the system. Authentication methods for NAC include, but are not limited to, Kerberos, MAC, or other protocols. The IP Assignment Forescout configuration ensures any IP addresses that should be managed by the configured network will go through the policies within Forescout. Forescout policy structure is applied in a "waterfall" like way that assures all IP addresses start with the top most policy and flow down the policy tree. This policy flow ensures that all endpoints are properly identified, classified, and authenticated prior to the posture assessment.

MAB is only one way of connecting non-entity endpoints, and can be defeated by spoofing the MAC address of an assumed authorized device. By adding the device to the MAB, the device can then gain access to the network. NPE devices that can support PKI or an allowed authentication type must use PKI. MAB may be used for NPE that cannot support an approved device authentication. Non-entity endpoints include Internet of Things (IoT) devices, VoIP phone, and printer.

Ensuring the proper amount of information is provided to the Security Management staff is imperative to ensure role based access control. Only those individuals that need to know about a security error of an application need to be notified of the error.

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 this notification, the security personnel may be unaware of an impending failure of the audit capability and system operation may be adversely affected. Note that this configuration allows for the central log server to be configured with a critical alert to be sent to the System Security Officer (ISSO) and Systems Administrator (SA) (at a minimum) if it is unable to communicate the Forescout or stops receiving log updates. The alert requirement is in the Syslog STIG.

Limiting the number of registered MAC addresses on a switch access port can help prevent a CAM table overflow attack. This type of attack lets an attacker exploit the hardware and memory limitations of a switch. If there are enough entries stored in a CAM table before the expiration of other entries, no new entries can be accepted into the CAM table. An attacker will be able to flood the switch with mostly invalid MAC addresses until the CAM table's resources have been depleted. When there are no more resources, the switch has no choice but to flood all ports within the VLAN with all incoming traffic. This happens because the switch cannot find the switch port number for a corresponding MAC address within the CAM table, allowing the switch to become a hub and traffic to be monitored. Some technologies are exempt from requiring a single MAC address per access port; however, restrictions still apply. VoIP or VTC endpoints may provide a PC port so a PC can be connected. Each of the devices will need to be statically assigned to each access port. Hot-desking is where several people are assigned to work at the same desk at different times, each user with their own PC. In this case, a different MAC address needs to be permitted for each PC that is connecting to the LAN drop in the workspace. Additionally, this workspace could contain a single phone (and possibly desktop VTC endpoint) used by all assignees, and the PC port on it might be the connection for their laptop. In this case, it is best not to use sticky port security but to use a static mapping of authorized devices. If this is not a teleworking remote location, this exemption does not apply.

In accordance with NIST SP 800-52, the TLS server must terminate the connection with a fatal “handshake failure” alert when a client certificate is requested and the client does not have a suitable certificate. During the TLS handshake negotiation, a "client certificate request" that includes a list of the types of certificates supported and the Distinguished Names of acceptable Certification Authorities (CAs) is sent to the client. TLS handshake enables the SSL or TLS client and server to establish the secret keys with which they communicate.

Using older unauthorized versions or incorrectly configuring protocol negotiation makes the gateway vulnerable to known and unknown attacks that exploit vulnerabilities in this protocol.

Forescout solution assesses the compliance posture of each client and returns an access decision based on configured security policy. The communications associated with this traffic must be protected from alteration and spoofing attacks so unauthorized devices do not gain access to the network.

Generating log records with regard to modules and policies is an important part of maintaining proper cyber hygiene. Keeping and maintaining the logs helps to establish, correlate, and investigate the events relating to an incident, or identify those responsible for one.

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 this notification, the security personnel may be unaware of an impending failure of the audit capability and system operation may be adversely affected. Audit processing failures include software/hardware errors, failures in the audit capturing mechanisms, and audit storage capacity being reached or exceeded. This requirement pertains to NAC types and threat protection events of events as opposed to device management events vs. operating system and system log types of events in the NDM check.

Continuous scanning capabilities on the NAC provide visibility of devices that are connected to the switch ports. The NAC continuously scans networks and monitors the activity of managed and unmanaged devices, which can be personally owned or rogue endpoints. Because many of today's small devices do not include agents, an agentless discovery is often combined to cover more types of equipment.

Without identifying devices, unidentified or unknown devices may be introduced, thereby facilitating malicious activity. Identification failure does not need to result in connection termination or preclude compliance assessment. This is particularly true for unmanaged systems or when the NAC is performing network discovery.

Bidirectional authentication provides stronger safeguards to validate the identity of other devices for connections that are of greater risk. Currently, DoD requires the use of AES for bidirectional authentication since it is the only FIPS-validated AES cipher block algorithm. Because of the challenges of applying this requirement on a large scale, organizations are encouraged to apply the requirement only to those limited number (and type) of devices that truly need to support this capability.