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Hardening OS X Using The NSA Guidelines

NSA Hardening Guidelines

The National Security Agency (NSA) has developed security hardening guidelines for various operating systems and technologies. I remember when I first started in information technology and used these guides to harden my Windows servers. I was met with mixed success; some systems would run better, and some would cease to function due to configuration changes. This taught me about my systems and their configurations, and knowing what your systems do and how they are configured is the true key to successful systems administration. Remember, the “guidelines” are just that, a guide to configuring and securing your systems. Ultimately, it is up to you to determine which changes you will implement, and most importantly test those changes in a lab/QA environment.


Mac OS X's popularity has been growing rapidly, and so has its use in corporate environments. The NSA has released a new hardening guide for OS X. Tenable has created a configuration audit that will compare the configuration of your OS X systems with the NSA's guidelines, and below are some of the example results from an audit:

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It’s not an every-day attack that is implemented by most common malware, but attackers could spy on you through the camera and microphone on your computer. I don't believe attackers will use this type of attack to collect massive amounts of sensitive information. However, someone could use it to violate your privacy, so it’s a good idea to disable audio and video input devices in your environment, as in rare cases someone could use them to literally "see" the inside of your organization.


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Attacks against the Bluetooth protocol are typically not given a high priority within organizations with respects to security. Bluetooth can be used by attackers, in certain circumstances, to transfer files, sniff keystrokes, or impersonate devices to inject keystrokes. I use a Bluetooth mouse with my laptop, which means I have to enable Bluetooth services. However, by changing my location in OS X, I can disable Bluetooth when I am traveling or away from home. Disabling it altogether might now work for you, so if you need it look into configuring locations on your OS X systems.

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Many administrators forget that OS X (along with Linux and Windows) enables IPv6 on network adapters by default. If you are using IPv6, configure it properly by making sure that the firewall is enabled for both IPv4 and IPv6. If you are not using IPv6, disable it. Attackers will use IPv6 to attack systems, relying on the lack of a firewall being able to stop packets using IPv6 if its not configured to do so (on either the network, the host, or both).

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The mDNS responder is responsible for the multicast DNS protocol, which tends to leak information such as operating system version and type on the network. It is interesting to note that it does this over multicast so there are no packets sent directly to the end host in certain configurations. Disabling unnecessary services goes a long way to help you harden your systems and improve performance.


Configuration auditing is an important process to any organization. Many organizations will state, "All my systems have X". Then they use Nessus to scan and audit their systems and typically find some systems that have fallen outside of their standards. There are a lot of moving parts to today's networks, and constant auditing and checking of your configurations is key to maintaining a secure environment.

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