CompTIA CSA+ Study Guide. Mike Chapple

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      Cybersecurity professionals use risk management strategies, such as risk acceptance, risk avoidance, risk mitigation, and risk transference, to reduce the likelihood and impact of risks identified during risk assessments. The most common way that organizations manage security risks is to develop sets of technical and operational security controls that mitigate those risks to acceptable levels.

      Technical controls are systems, devices, software, and settings that work to enforce confidentiality, integrity, and/or availability requirements. Examples of technical controls include building a secure network and implementing endpoint security, two topics discussed later in this chapter. Operational controls are practices and procedures that bolster cybersecurity. Examples of operational controls include conducting penetration testing and using reverse engineering to analyze acquired software. These two topics are also discussed later in this chapter.

      Building a Secure Network

      Many threats to an organization’s cybersecurity exploit vulnerabilities in the organization’s network to gain initial access to systems and information. To help mitigate these risks, organizations should focus on building secure networks that keep attackers at bay. Examples of the controls that an organization may use to contribute to building a secure network include network access control (NAC) solutions; network perimeter security controls, such as firewalls; network segmentation; and the use of deception as a defensive measure.

      One of the basic security objectives set forth by most organizations is controlling access to the organization’s network. Network access control (NAC) solutions help security professionals achieve two cybersecurity objectives: limiting network access to authorized individuals and ensuring that systems accessing the organization’s network meet basic security requirements.

The 802.1x protocol is a common standard used for NAC. When a new device wishes to gain access to a network, either by connecting to a wireless access point or plugging into a wired network port, the network challenges that device to authenticate using the 802.1x protocol. A special piece of software, known as a supplicant, resides on the device requesting to join the network. The supplicant communicates with a service known as the authenticator that runs on either the wireless access point or the network switch. The authenticator does not have the information necessary to validate the user itself, so it passes access requests along to an authentication server using the RADIUS protocol. If the user correctly authenticates and is authorized to access the network, the switch or access point then joins the user to the network. If the user does not successfully complete this process, the device is denied access to the network or may be assigned to a special quarantine network for remediation. Figure 1.5 shows the devices involved in 802.1x authentication.

Figure 1.5 In an 802.1x system, the device attempting to join the network runs a NAC supplicant, which communicates with an authenticator on the network switch or wireless access point. The authenticator uses RADIUS to communicate with an authentication server.

      There are many different NAC solutions available on the market, and they differ in two major ways:

      Agent-Based vs. Agentless Agent-based solutions, such as 802.1x, require that the device requesting access to the network run special software designed to communicate with the NAC service. Agentless approaches to NAC conduct authentication in the web browser and do not require special software.

      In-Band vs. Out-of-Band In-band (or inline) NAC solutions use dedicated appliances that sit in between devices and the resources that they wish to access. They deny or limit network access to devices that do not pass the NAC authentication process. The “captive portal” NAC solutions found in hotels that hijack all web requests until the guest enters a room number are examples of in-band NAC. Out-of-band NAC solutions, such as 802.1x, leverage the existing network infrastructure and has network devices communicate with authentication servers and then reconfigure the network to grant or deny network access, as needed.

      NAC solutions are often used simply to limit access to authorized users based on those users successfully authenticating, but they may also make network admission decisions based on other criteria. Some of the criteria used by NAC solutions include:

      Time of Day Users may be authorized to access the network only during specific time periods, such as during business hours.

      Role Users may be assigned to particular network segments based on their role in the organization. For example, a college might assign faculty and staff to an administrative network that may access administrative systems while assigning students to an academic network that does not allow such access.

      Location Users may be granted or denied access to network resources based on their physical location. For example, access to the datacenter network may be limited to systems physically present in the datacenter.

      System Health NAC solutions may use agents running on devices to obtain configuration information from the device. Devices that fail to meet minimum security standards, such as having incorrectly configured host firewalls, outdated virus definitions, or missing patches, may be either completely denied network access or placed on a special quarantine network where they are granted only the limited access required to update the system’s security.

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