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This chapter is from the book

Begin by Laying the Framework

Businesses have two key areas of interest for their self-defending network: protecting their assets and thwarting misbehavior.

Asset Protection

Most businesses already have a software patch management process in place. Integrating software patch management processes with NAC can significantly improve the effectiveness of those processes. Before NAC, software compliance was not easily enforceable because host posturing did not exist. Users could stop updates from occurring or decide to update when they had time, which allows malware to spread even when software updates were made available to prevent such an outbreak. Being able to enforce software patch compliance is one of the initial major drivers for implementing NAC.

Cisco offers two network admission control choices: NAC Framework and NAC Appliance. Traditionally, businesses adopt one of the two models.

Many businesses initially adopt the NAC Appliance method, which provides a simpler approach to detection and enforcement of host software. NAC Appliance is an all-in-one solution that allows a rapid deployment model using a self-contained endpoint assessment, policy management, and remediation services. It provides similar operating system compliance checks and policy enforcement but can operate in a multivendor network infrastructure. It does not use an integrated approach with NAC partners that provide additional host posturing and enforcement functionality like NAC Framework. Also, at the time of this writing, identity enforcement is not available with NAC Appliance.

Others might want to add more admission checks, such as identity and corporate asset enforcement, migrating to an integrated environment as their deployments and requirements mature.

NAC Framework uses an integrated approach, leveraging infrastructure that is used as the policy enforcement point. NAC Framework also leverages existing security solutions from other vendors, such as antivirus, remediation, patching, and auditing services. The NAC Framework model allows a more flexible admission policy that is typically more complex than NAC Appliance deployments.

With NAC Framework, in addition to software compliance, you can add Identity-Based Networking Services (IBNS) to your admission policy decision when using NAC-L2-802.1X. Combining user and host authentication as part of the network admission decision is the strongest authorization model. With today’s mobile workforces, you need to control who can gain access to different parts of the network. Your policy might need to differ based on a wired or wireless device. With identity as part of the admission policy, you can provide predetermined IP addresses only to valid users and devices that successfully authenticate and have been verified as being compliant.

Many NAC partners provide IBNS capabilities that can plug into the NAC Framework today. For example, some IBNS solutions assign rights to resources based on the identity of a user, specifying the user’s network access, shared resource access to servers and printers, access for file read and/or write, and ability to use specific software applications.

You might need an admission policy that can assign the appropriate rights based on when a device is used, where a device or user is physically located, or a combination of when, where, and who. Examples include the following:

  • Internal wired policy versus wireless policy.
  • Geography-based policy to preserve confidentiality of data by enforcing whether it can be accessed and/or retrieved based on host location. Different policies might be needed for:
    • — VPN access from a public area, such as the airport, hotel, or coffee shop.
    • — VPN access from a more private place, such as a remote or home office.
    • — Region-based access to limit remote users from accessing locally significant information, such as files not allowed for export.
    • — Time-of-day and day-of-week policy to limit access to sensitive areas outside normal business hours.

You can determine how you plan to enforce compliance on devices that you don’t manage or control. You can determine whether you are going to include the ability to exempt devices that cannot interwork with NAC so that they can use the network. Different methods exist to accomplish registering and exempting devices that can’t communicate their credentials. You can use a dynamic auditing strategy to scan unmanaged devices, or you can statically maintain an exception table.

Use NAC Framework if your initial NAC deployment requires the following:

  • Deep vendor integration for assessment and/or remediation
  • 802.1X for initial NAC deployment
  • Too many NAC appliance servers and overlay devices to satisfy admission control solution for a large enterprise

If a rapid deployment model is required or a simpler management method is desired, use the NAC Appliance. It uses the Cisco Clean Access product to provide out-of-the-box functionality with preinstalled support for antivirus and Microsoft updates.

NAC Appliance uses a turnkey approach versus the more complex feature-rich NAC Framework model. While many see the value of NAC Framework, some don’t need all the other capabilities today and prefer a more simplistic approach.

Cisco plans to move forward with additional features in both models as well as to build a tighter integration between NAC Framework and NAC Appliance. Both architectures will be able to coexist and be centrally managed by a common management interface.

Detecting Misbehavior and Dealing with It

Other components of the self-defending network can be optionally implemented to detect and defend against malicious behavior. Misbehavior can exist in many forms. It can be intentional or nonintentional actions from users, failing or compromised devices, or external misbehavior from hackers. Examples include the following:

  • Using an intrusion protection system (IPS), such as a network-based IPS (NIPS) or host-based IPS (HIPS), to defend in depth against misbehavior on the network and individual hosts—An example of a HIPS is Cisco Security Agent (CSA) running on hosts that function as PCs and servers. CSA can recognize application behavior that can lead to an attack and can prevent its malicious activity. You can create custom profiles for the different roles of servers and users, providing various levels of protection based on device use. For example, servers used as shared resources might require a fixed and hardened security policy, such as not allowing software applications to be installed, preventing system configuration files from being altered, and not opening TCP ports other than the ones needed for the server’s applications. In contrast, hosts operated by some users might need to add software to perform their jobs, while other users are not allowed to add software. Any behavior attempted beyond the profile’s acceptable policy is not allowed. Use NAC to enforce the use of the HIPS application by making sure that it is enabled and up to date before allowing the host to access the network. For example, with the integration of NAC and CSA, dynamic policy decisions can be made based on information provided from CSA.

  • Using Cisco Secure Monitoring, Analysis, and Response System (CS-MARS) to analyze, monitor, and detect all types of events on your network and present them in a single networkwide topology view—CS-MARS can detect anomalies that could be caused by a host generating huge amounts of traffic because of a worm infection. CS-MARS can work with the policy server to automatically shut down the affected section of the network to reduce exposure to others, shun an offending device, or force device remediation. Beginning with version 4.1, CS-MARS can correlate and report on IOS-based 802.1X authentication events from IOS, CatOS, and Access Control Server (ACS) devices. As a result, CS-MARS can act as the centralized NAC reporting engine for security operators to monitor authentication and device posturing policies. CS-MARS has many predefined NAC reports that can be easily interpreted by a help desk operator, providing a quick summary in a graphical view. For example, compliance reports can identify healthy or unhealthy devices. If more information is needed, the operator can query for details about the host or user to diagnose the problem.

  • Using Cisco IOS NetFlow, which is available in routers, to provide visibility across the entire network, capturing traffic data to aid in understanding typical traffic trends—Changes in network behavior can indicate denial of service (DoS) attacks or anomalies such as viruses and worms. NetFlow works by tracking packet flows between a given source and destination, which helps identify the path an attack is taking through the network. The NetFlow data can be exported and used by other applications or network management technologies such as CS-MARS.

These additional self-defending network technologies work in harmony with NAC and extend its capability by proactively protecting and defending the network, hosts, and users against misbehavior.

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