Components That Make Up the NAC Framework Solution

1. Cisco Network Admission Control Agent Software For Mac Pro
2. Cisco Network Admission Control Agent Software For Mac Os

The following sections examine the individual components that make up the NAC Framework solution. Although only an overview is provided here, each component is covered in detail in its associated chapter in this book.

The Cisco Network Admission Control (NAC) agent on Mac OS X does not verify the X.509 certificate of an Identity Services Engine (ISE) server during an SSL session, which allows man-in-the-middle attackers to spoof ISE servers via an arbitrary certificate, aka Bug ID CSCub24309. Baseline Network Admission Control based on users, ports, and MAC addresses Easy network configuration, Cisco IOS Software updates, and troubleshooting using Cisco Network Assistant software QoS for traffic classification and shaping to prioritize various applications.

Gartner defines network access control (NAC) as technologies that enable organizations to implement policies for controlling access to corporate infrastructure by both user-oriented devices and Internet of Things (IoT) devices. Policies may be based on authentication, endpoint configuration (posture) or users' role/identity. Cisco NAC Agent The Cisco NAC Agent, also referred to as the Clean Access Agent or Software Agent, is a Cisco-provided, free software program that resides on client PCs. Its purpose is to gather information about the user and device on which it is installed. It runs on a variety of endpoint machines (Windows, Mac) and is provisioned over the web. Title: NAC-Architecture-CMUG-forpdf Compatibility Mode Author: rchee Created Date: 1/21/2009 10:33:18 AM.

Cisco Trust Agent

Cisco Trust Agent (CTA) is a small software application (approximately 3MB) that is installed locally on a PC and that allows Cisco Secure ACS to communicate directly with the PC to query it for posture credentials. Some common posture credentials are the OS name, the service pack installed, and specific hotfixes applied. Table 1-1 lists the posture credentials that CTA supports or for which CTA is a broker.

Table 1-1. Posture Credentials Supported by CTA

CTA is a core component of NAC and is the only communications interface between the NAD and the applications that reside on the PC. It receives posture credential queries from Cisco Secure ACS, brokers them to the correct application, and then forwards the application responses to Cisco Secure ACS. CTA has three key responsibilities (see Figure 1-4):

• Communication—Provides a communications link with the NAD using EAPoUDP or EAP-FAST.
• Security—Authenticates the device requesting posture credentials and ensures that all information is sent out encrypted on the wire.
• Broker—Provides an application programming interface (API) to query other applications running on the system and notifies them of the current system posture so they can react to posture changes.

CTA also includes an 802.1X supplicant bundled with it that supports EAP-FAST when running NAC. The 802.1X supplicant is needed to implement NAC-L2-802.1X. However, the 802.1X supplicant is limited to wired interfaces only—no wireless interfaces.

Chapter 2, 'Cisco Trust Agent,' fully covers the installation, configuration, operation, and troubleshooting of CTA.

Cisco Security Agent

Cisco Security Agent (CSA) is the Cisco award-winning host-based intrusion-prevention system (HIPS) installed on a desktop or server PC that protects it from known and unknown threats. CSA adds a shim into the network layer and into the kernel layer (to watch both network traffic and API calls to kernel). This allows CSA to not only be a personal firewall, but also to protect against buffer-overflow attacks and spyware/adware. In addition, it provides file protection, malicious application protection, and operating-system integrity protection. CSA is one of the few HIPS products that provide true protection against 'Day Zero' attacks.

Starting with version 4.5, CSA integrates seamlessly with NAC through CTA. CTA queries CSA to establish the presence of the agent and determine whether it is in protect mode. This information is part of the posture credentials returned to Cisco Secure ACS and is used to determine the end host's overall security posture. Based on this posture, Cisco Secure ACS can apply a policy that alters the state of CSA. CSA's state change dynamically activates additional rules within CSA, thereby providing another level of protection to the host.

Cisco Security Agent Management Center (CSA MC) provides a powerful, scalable application used to manage all agents. When an agent is installed on a host, it first registers with CSA MC and downloads any updates to its rule set. Thereafter, the agent periodically polls CSA MC to check for any new software or rule updates. Besides the configuration and software update function, CSA MC receives real-time security events from the agents and immediately displays them in the Event Monitor for the network administrator to see. In addition, CSA MC correlates the events, received from all agents in the network, to detect suspicious activity across several hosts. If similar threats are detected across several agents, CSA MC creates and deploys dynamic rules to all the agents to provide an additional layer of protection against this newly spreading threat.

Chapter 9, 'Cisco Security Agent,' covers the installation, configuration, and operation of CSA.

See Chapter 9 for installation and configuration information about CSA and CSA MC.

Network-Access Devices

NADs query the CTA installed on the endpoint. In NAC Phase I, the NAD could be only an IOS router. In Phase II, any of the following devices can be a NAD:

• Cisco IOS router
• Cisco Catalyst Switch running Cisco IOS or CAT OS
• Cisco VPN 3000 series concentrator
• Cisco ASA 5500 series adaptive security appliances and PIX 500 series security appliances
• Cisco wireless access device

Cisco IOS Router

Cisco IOS routers first supported NAC in Cisco IOS Release 12.3(8)T, in the Advanced Security, Advanced IP Services, or Advanced Enterprise Services feature sets. Table 1-2 lists Cisco IOS routers by platform and current NAC capability.

Table 1-2. NAC Support in IOS Routers

When NAC is implemented on a router, this is called NAC-L3-IP. That is, the security enforcement point becomes the Layer 3 gateway instead of the physical port into which the end host is plugged.

Posture validation is triggered by defining an intercept ACL on the router's interface. Any traffic arriving on the interface from a nonpostured source that matches the intercept ACL triggers the posture-validation process, as illustrated in Figure 1-1. When the overall security posture of the host is determined, Cisco Secure ACS sends a host-based downloadable ACL to the router to restrict, prohibit, or permit that client's access to the network. Thus, policy enforcement takes place at Layer 3 with an ACL on the router's interface.

See Chapter 5, 'Configuring Layer 3 NAC on Network-Access Devices,' for more information on configuring and troubleshooting NAC on a Cisco IOS router.

Cisco Catalyst Switch Running Cisco IOS or CAT OS

Catalyst switches first supported NAC in the summer of 2005 across various platforms and release trains. One benefit of adding NAC on the switch is enhanced posture-enforcement capabilities through containment. On Cisco IOS routers, policy enforcement was applied with a downloadable ACL on the router's interface. This enabled the administrator to restrict (or even deny) the endpoint's access through the router. However, the endpoint could not be restricted from sending packets to Layer 2–adjacent devices (because those packets did not traverse the router and, therefore, would not be subject to the downloadable ACL). However, on access switches, the endpoints are typically directly connected to a physical port on the switch. This allows for policy enforcement (through VLAN or ACL) as well as containment (because the endpoint is typically the only device connected to that port).

Catalyst switches can implement NAC on a per-port basis at Layer 2 or Layer 3. As mentioned previously in this chapter, when NAC is implemented at Layer 2, it is known as NAC-L2-802.1X because 802.1X is used as the underlying Layer 2 transport protocol. When NAC is implemented on a switch at Layer 3, it is known as NAC-L2-IP.

NAC-L2-802.1X and NAC-L2-IP have several administrative and operational differences that you should fully consider before selecting which one to deploy.

The following are attributes of NAC-L2-802.1X:

• 802.1X authentication must be implemented on the switch.
• The client's 802.1X supplicant triggers authentication and posture validation.
• The client's 802.1X supplicant must be CTA aware.
• Posture enforcement is provided by VLAN assignment only.
• EAP-FAST authenticates CTA to Cisco Secure ACS; therefore, no client-side certificate is needed.
• Endpoints must be directly connected, or be connected through an IP phone.

The following are attributes of NAC-L2-IP:

• Posture validation is triggered when the switch receives Address Resolution Protocol (ARP) packets from the endpoint. Optionally, Dynamic Host Configuration Protocol (DHCP) snooping can be enabled on the port to trigger posture validation when the switch receives the first DHCP packet.
• Posture enforcement is provided by downloadable ACLs.
• VLAN assignment is not supported.
• EAPoUDP is used to communicate between CTA and the NAD. PEAP is used between CTA and Cisco Secure ACS.
• URL redirection of the endpoint's web browser to a remediation server is supported.
• Endpoints can be directly connected, connected through an IP phone, or connected through a shared-media device (hub, non-NAC-capable switch, and so on.)

No 'right' or 'wrong' choice exists between the two. But there is a best choice for your network. If you don't know what that choice is, read Cisco Network Admission Control, Volume I: NAC Architecture and Design, which walks through several design scenarios, discusses the options available, and provides the rationale for the choices made.

An additional consideration (and probably the most important one) is which one will run on your existing switch hardware. Table 1-3 should come in handy in making that determination; it lists the various models of Catalyst switches and their NAC capabilities based on the OS.

Table 1-3. NAC Support in Catalyst Switches

Catalyst switches are an integral part of the NAC solution, providing protection and containment of hosts that do not meet corporate security policies at the access layer. As such, Cisco is committed to providing NAC support on all new switch hardware.

See Chapter 4 for more information on configuring and troubleshooting NAC on a Catalyst switch.

Cisco VPN 3000 Series Concentrator

NAC support for the VPN 3000 series concentrators was first added in Release 4.7. The concentrator is a Layer 3 NAD and postures remote-access IPSec (or Layer 2 Tunneling Protocol [L2TP] over IPSec) clients. The posturing process is almost identical to that of NAC-L3-IP, described previously in the section 'NAC: Phase I' (refer to Figure 1-1). The only difference is that the router is replaced with a VPN 3000 concentrator, and an IPSec tunnel is first established to the concentrator before the EAPoUDP session starts.

When the EAPoUDP session starts, a PEAP session is established between the client and the Cisco Secure ACS so posture validation can take place. Cisco Secure ACS then notifies the concentrator (through RADIUS) of the client's posture and passes down a filter list to be applied to the client. The filter list is the 3000's equivalent to a downloadable ACL.

One unique option that the concentrator provides is that clients can be excluded from posture validation based solely on OS type. This is because the Cisco VPN client sends its OS information during IPSec tunnel establishment, which occurs before NAC posture validation. Host exemption, along with all other NAC configuration, is specified under the group policy settings on the 3000. NAC configuration on the VPN 3000 concentrator is covered in detail in Chapter 6, 'Configuring NAC on Cisco VPN 3000 Series Concentrators.'

Cisco ASA 5500 Series Adaptive Security Appliance and PIX 500 Series Security Appliance

The NAC implementation on the Cisco 5500 series Adaptive Security Appliances (ASA) and PIX 500 series security appliances is identical to the implementation on the VPN 3000 concentrators. NAC-L3-IP is supported starting with Version 7.2(1) on all IPSec and L2TP over IPSec remote-access tunnels. Posture enforcement is provided by way of a downloadable ACL from Cisco Secure ACS. Additionally, just as with the VPN 3000, remote-access clients can be exempted from NAC posture validation based on OS type.

The ASA and PIX also support clientless authentication. Those hosts connecting through a remote-access tunnel that do not have CTA installed are marked as clientless. Cisco Secure ACS can then apply the clientless policy to those hosts, to limit (or remove entirely) their access to the network. Chapter 7, 'Configuring NAC on Cisco ASA and PIX Security Appliances,' contains the complete configuration of NAC on the ASA 5500 series appliances and PIX 500 series security appliances.

Cisco Wireless Devices

NAC Framework support for wireless devices is available on autonomous Access Points (AP), lightweight access points running the Lightweight Access Point Protocol (LWAPP), and the Wireless LAN Services Module (WLSM) for the Catalyst 6500. Table 1-4 lists the wireless devices and minimum supported software.

Table 1-4. NAC Support in Wireless Devices

Wireless devices are Layer 2 termination devices and, as such, support NAC-L2-802.1x as the posturing method. The process that a wireless client connecting to a wireless device goes through for posture validation is the same as for a wired client. Figure 1-3 depicts this posture. Note that wireless devices provide posture enforcement through VLAN only. This means that, to support NAC, the wireless devices must be configured for multiple VLANs per service set identifier (SSID).

Configuration and troubleshooting of NAC on Cisco wireless access points is covered along with other Layer 2 network-access devices in Chapter 4.

Cisco Secure Access Control Server

The Cisco Secure Access Control Server (ACS) for Windows is another core required component of NAC. Cisco Secure ACS first supported NAC in Version 3.3, which was launched concurrently with Phase I in the summer of 2004. Cisco Secure ACS 4.0, released in the fall of 2005, added support for NAC Phase II, including all the NADs listed in the previous section.

Cisco Secure ACS is the central controller for all NAC policy decisions. It receives posture credentials from all agents and either processes them locally or forwards them on to partner validation servers for processing. If the posture credentials are forwarded on, Cisco Secure ACS waits to receive the application posture token (APT) back from the external validation server. It then combines this APT with the local APTs it created based on the defined policy; the result is an overall system posture token (SPT).

The SPT has one of the following values: Healthy, Checkup, Quarantine, Infected, or Unknown, which are mapped to a network access policy. The network-access policy and SPT are then transmitted to the NAD as part of policy enforcement. Optionally, Cisco Secure ACS can send a user-notification message that CTA displays on the end host. This message usually indicates the posture of the system along with some instructions (for the un-Healthy hosts). Cisco Secure ACS can also send a URL redirect to the end host via the NAD if either NAC-L3-IP or NAC-L2-IP is being used.

Chapter 8 covers installation, configuration, and troubleshooting of Cisco Secure ACS.

Event Monitoring, Analysis, and Reporting

Protecting the network from threats is the first step toward securing it. However, event monitoring, analysis, and reporting are also vital pieces in understanding the network's security posture:

• Event monitoring—The process of receiving events (or alerts) from the network and presenting them to the user in real time and in a meaningful way. This is usually provided with some sort of 'dashboard' where new events are displayed as they come in.
• Analysis—The process of taking the events received and normalizing and correlating them to produce the most relevant set of data. The correlation process takes multiple streams of events from various device types and finds similarities in their data that can be linked to provide a detailed composite picture. The normalization process then removes the redundant data and improves data consistency.
• Reporting—The process of querying historical data for specific events and presenting those events in a useful way to the user.

Monitoring, analysis, and reporting are powerful tools that show the network administrator the state of the network at any given point in time. These tools are very important in networks where NAC is enabled because the volume of events that each network device generates for each postured host is huge. Monitoring the network devices individually for problems or anomalies is neither practical nor efficient. This is why Cisco has enhanced its Cisco Security Monitoring, Analysis, and Reporting System (CS-MARS) to support NAC.

The CS-MARS appliance is a topologically aware, high-performance event-correlation system. Syslogs, NetFlow data, Simple Network Management Protocol (SNMP) traps, and other network logging information can be sent to it from a variety of network sources. This includes routers, switches, firewalls, intrusion-prevention devices, Cisco Secure ACS, and even end hosts. All this information is then correlated within CS-MARS to detect network attacks and other types of security threats. When an attack is detected, an incident is fired and the attacker, victim, and path from attacker to victim are displayed in the CS-MARS interface. Additionally, based on the attack vector, CS-MARS can inform the user of the best way to mitigate the attack.

In support of NAC, CS-MARS parses, normalizes, correlates, and reports on posture-validation events for NAC-L3-IP, NAC-L2-IP, and NAC-L2-802.1X. Predefined reports enable network administrators to view the number of hosts in Healthy, Quarantined, Clientless, or other states throughout the entire network. Administrators can further drill down to determine the posture status on a per-device basis. They may also choose to receive daily reports (via e-mail) of the number and location of nonhealthy hosts in their network.

Help-desk support teams can use CS-MARS to identify problems reported from end users. CS-MARS can display IP addresses, machine/usernames, and the logical switch port number the user is connected to, along with the posture information or authentication information of end hosts. This information can be displayed in real time and allows the help-desk teams to quickly and easily identify problems end users are having.

Chapter 17, 'Monitoring the NAC Solution Using the Cisco Security Monitoring, Analysis, and Response System,' covers the configuration and operation of CS-MARS in a NAC Framework solution.

Cisco NAC Appliance, formerly Cisco Clean Access (CCA), was a network admission control (NAC) system developed by Cisco Systems designed to produce a secure and clean computer network environment. Originally developed by Perfigo and marketed under the name of Perfigo SmartEnforcer, this network admission control device analyzes systems attempting to access the network and prevents vulnerable computers from joining the network. The system usually installs an application known as the Clean Access Agent on computers that will be connected to the network. This application, in conjunction with both a Clean Access server and a Clean Access Manager, has become common in many universities and corporate environments today. It is capable of managing wired or wireless networks in an in-band or out-of-band configuration mode, and Virtual Private networks (VPN) in an in-band only configuration mode.

Cisco NAC Appliance is no longer in production and no longer sold as of the early 2010s. Mainstream support ending in 2015. Extended support ending in 2018.

Clean Access Agent[edit]

The Clean Access Agent (abbreviation: CCAA, 'Cisco Clean Access Agent') resides on the client's machine, authenticates the user, and scans for the required patches and software. Currently the Clean Access Agent application is only available for some Windows and Mac OS X operating systems (Windows 98, Windows Me, Windows 2000, Windows XP, Windows XP Media Center Edition, Windows Vista, Windows 7, Windows 8 and Mac OS X);^[1] most network administrators allow clients with non-Windows operating systems (such as Mac OS 9, Linux, and FreeBSD) to access the network without any security checks (authentication is still required and is usually handled via a Web interface).

Authentication[edit]

After successfully authenticating via a web interface, the Clean Access Server will direct new Windows based clients to download and install the Clean Access Agent application (at this time, non-Windows based clients need only authenticate via the web interface and agree to any network terms of service). Once installed, the Agent software will require the user to re-authenticate. Once re-authenticated, the Agent software will typically check the client computer for known vulnerabilities to the Windows operating system being used, as well as for updated anti-virus software and definitions. The checks are maintained as a series of 'rules' on the Clean Access Manager side. The Clean Access Manager (CAM) can be configured to check, install, or update anything on the user's system. Once the Agent application checks the system, the Agent will inform the user of the result – either with a success message, or a failed message. Failed messages inform the user of what category(s) the system failed (Windows updates, antivirus, etc.), and instruct the user on how to proceed.

Any system failing the checks will be denied general access to the network and will probably be placed in a quarantined role (how exactly a failed system is handled depends entirely on how the Clean Access Manager is configured, and may vary from network to network. For example: a failed system may simply be denied all network access afterward). Quarantined systems are then typically given a 60-minute window where the user can try to resolve the reason(s) for quarantine. In such a case, the user is only allowed connectivity to the Windows Update website and a number of antivirus providers (Symantec, McAfee, Trend Micro, etc.), or the user may be redirected to a Guest Server for remediation. All other traffic is typically blocked. Once the 60-minute window expires, all network traffic is blocked. The user has the option of re-authenticating with Clean Access again, and continuing the process as needed.

Systems passing the checks are granted access to the network as defined by the assigned role on the Clean Access Manager. Clean Access configurations vary from site to site. The network services available will also vary based on Clean Access configuration and the assigned user role.

Systems usually need to re-authenticate a minimum of once per week, regardless of their status; however, this option can be changed by the network administrator. Also, if a system is disconnected from the network for a set amount of time (usually ten minutes), the user will have to re-authenticate when they reconnect to the network.

Windows Updates[edit]

Clean Access normally checks a Windows system for required updates by checking the system's registry. A corrupted registry may keep a user from being able to access the network.

Security Issues and Concerns[edit]

User Agent Spoofing[edit]

The Clean Access Server (CAS) determines the client's operating system by reading the browser's user agent string after authentication. If a Windows system is detected, then the server will ask the user to download the Clean Access Agent; on all other operating systems, login is complete. To combat attempts to spoof the OS in use on the client, newer versions of the Server and Agent (3.6.0 and up) also probe the host via TCP/IP stack fingerprinting and JavaScript to verify the machine's operating system:

By default, the system uses the User-Agent string from the HTTP header to determine the client OS. Release 3.6.0 provides additional detection options to include using the platform information from JavaScript or OS fingerprinting from the TCP/IP handshake to determine the client OS. This feature is intended to prevent users from changing identification of their client operating systems through manipulating HTTP information. Note that this is a 'passive' detection technique that only inspects the TCP handshake and is not impacted by the presence of a firewall.^[2]

Microsoft Windows Scripting[edit]

The Clean Access Agent makes extensive use of the Windows Script Engine, version 5.6. It was demonstrated that removal or disabling of the scripting engine in MS Windows will bypass and break posture interrogation by the Clean Access Agent, which will 'fail open' and allow devices to connect to a network upon proper authentication.^[3]

MAC Spoofing Prevention[edit]

Device Segregation[edit]

While MAC address spoofing may be accomplished in a wireless environment by means of using a sniffer to detect and clone the MAC address of a client who has already been authorized or placed in a 'clean' user role, it is not easy to do so in a wired environment, unless the Clean Access Server has been misconfigured. In a correct architecture and configuration, the Clean Access Server would hand out IP subnets and addresses via DHCP on its untrusted interface using a 30-bit network address and 2 bits for hosts, therefore only one host could be placed in each DHCP scope/subnet at any given time. This segregates unauthorized users from each other and from the rest of the network, and makes wired-sniffing irrelevant and spoofing or cloning of authorized MAC addresses nearly impossible. Proper and similar implementation in a wireless environment would in fact contribute to a more secure instance of Clean Access.

Certified-Device Timers[edit]

In addition, MAC-spoofing could further be combated with the use of timers for certified devices. Timers allow administrators to clear the list of certified MAC addresses on a regular basis and force a re-authorization of devices and users to the Clean Access Server. Timers allow an administrator to clear certified devices based on user roles, time and date, and age of certification; a staggered method is also available that allows one to avoid clearing all devices at once.

Complaints[edit]

Cisco NAC Appliance is notorious^{[weasel words]} for creating disruptions in the Internet connections of users, considering a continuous connection between a computer and a server or another computer as suspicious activity. This is problematic for individuals using Skype or any webcam activity as well as online games such as World of Warcraft. With online games, the disruptions created by Cisco NAC Appliance cause the player to be logged off the gaming server. Numerous individuals who have experienced this rather blunt manner of security have openly expressed frustration with this software in forums as well as on Facebook with groups and posts.^[4]

References[edit]

1. ^'Support Information for Cisco NAC Appliance Agents, Release 4.5 and Later'. cisco.com.
2. ^'Release Notes for Cisco Clean Access (NAC Appliance) Version 3.6(4)'. Archived from the original on 2006-08-29.
3. ^'Release Notes for Cisco NAC Appliance (Cisco Clean Access), Version 4.1(2)'. Archived from the original on 2007-10-12.
4. ^'CCIE Labs Workbook'. Retrieved 15 Feb 2018.

Cisco Network Admission Control Agent Software For Mac Pro

External links[edit]

• Clean Access Administrators Mailing List – Archives hosted by Miami University
• Cisco Security Response – Cisco's Response to the latest NAC Agent Installation Bypass vulnerability

Cisco Network Admission Control Agent Software For Mac Os