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ESF: Controls: Secure Configurations

By Mike Rothman

Now that we’ve established a process to make sure our software is sparkly new and updated, let’s focus on the configurations of the endpoint devices that connect to our networks. Silly configurations present another path of least resistance for the hackers to compromise your devices. For instance, there is no reason to run FTP on an endpoint device, and your standard configuration should factor that in.

Define Standard Builds

Initially you need to define a standard build, or more likely a few standard builds. Typically for desktops (no sensitive data, and sensitive data), mobile employees, and maybe, kiosks. There probably isn’t a lot of value to going broader than those 4 profiles, but that will depend on your environment.

A good place to start is one of the accepted benchmarks of configurations available in the public domain. Check out the Center for Internet Security, which produces configuration benchmarks for pretty much every operating system and many of the major applications. In order to see your tax dollars at work (if you live in the US anyway), also consult NIST, especially if you are in the government. Its SCAP configuration guides provide a similar type of enumeration of specific setting to lock down your machines.

To be clear, we need to balance security with usability and some of the configurations suggested in the benchmarks clearly impact usability. So it’s about figuring out what will work in your environment, documenting those configurations, getting organizational buy-in, and then implementing.

It also makes sense to put together a list of authorized software as part of the standard builds. You can have this authorized software installed as part of the endpoint build process, but it also provides an opportunity to revisit policies on applications like iTunes, QuickTime, Skype, and others which may not yield a lot of business value and have a history of vulnerability. We’re not saying these applications should not be allowed – you’ve got to figure that out in the context of your organization – but you should take the opportunity to ask the questions.

Anti-Exploitation

As you define your standard builds, at least on Windows, you should turn on anti-exploitation technologies. These technologies make it much harder to gain control of an endpoint through a known vulnerability. I’m referring to DEP (data execution prevention) and ASLR (address space layout randomization), though Apple is also implementing similar capabilities in their software.

To be clear, anti-exploitation technology is not a panacea for protection – as the winners of Pwn2Own at CanSecWest show us every year. Especially for those applications that don’t support it (d’oh!), but the technologies do help make it harder to exploit the vulnerabilities in compatible software.

Other Considerations

  • Running as a standard user – We’ve written a bit on the possibilities of devices running in standard user mode (as opposed to administrator mode), and you should consider this option when designing secure configurations, especially to help enforce authorized software policies.
  • VPN to Corporate – Given the reality that mobile users will do something silly and put your corporate data at risk, one technique to protect them is to run all their Internet traffic through the VPN to your site. Yes, it may add a bit of latency, but at least the traffic will be running through the web gateway and you can both enforce policy and audit what the user is doing. As part of your standard build, you can enforce this network setting.

Implementing Secure Configurations

Once you have the set of secure configurations for your device profiles, how do you start implementing them? First make sure everyone buys into the decisions and understands the ramifications of going down this path. Especially if you plan to stop users from installing certain software or block other device usage patterns. Constantly asking for permission can be dangerously annoying but choosing the right threshold for confirmations is a critical aspect of a designing a policy. If the end users feel they need to go around the security team and their policies to get the job done, everyone loses.

Once the configurations are locked and loaded, you need to figure out how much work is required for implementation. Next you assess the existing endpoints against the configurations. Lots of technologies can do this, ranging from Windows management tools, to vulnerability scanners, to third party configuration management offerings. The scale and complexity of your environment should drive the selection of the tool.

Then plan to bring those non-compliant devices into the fold. Yes, you could just flip the switch and make the changes, but since many of the configuration settings will impact user experience, it makes sense to do a bit of proactive communication to the user community. Of course some folks will be unhappy, but that’s life. More importantly, this should help cut down help desk mayhem when some things (like running that web business from corporate equipment) stop working.

Discussion of actually making the changes brings us to automation. For organizations with more than a couple dozen machines, a pretty significant ROI is available from investing in some type of configuration management. Again, it doesn’t have to be the Escalade of products, and you can even look at things like Group Policy Objects in Windows. The point is making manual changes on devices is idiotic, so apply the level of automation that makes sense in your environment.

Finally, we also want to institutionalize the endpoint configurations, and that means we need to get devices built using the secure configuration. Since you probably have an operations team that builds the machines, they need to get the image and actually use it. But since you’ve gotten buy-in at all steps of this process, that shouldn’t be a big deal, right?

Next up, we’ll discuss the anti-malware space and what makes sense on our endpoints.


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Comments

Anything we can do at the application layer to further reduce the ability of attackers to corrupt the internals of the device are good things. So buffer overflow protection and kernel memory protection would be great, but that involves the application to be developed with those in mind. Likewise, applications must leverage DEP and ASLR in order to take advantage of those operating system level protections.

These techniques are quite effective at stopping many of the attack vectors that provide access to the device—but not all. And from an efficiency standpoint, I don’t think an end user would be able to tell the difference in application performance or responsiveness.

But we can’t assume that the application will take advantage of these security techniques (like many don’t check for SQL Injection or XSS vulnerabilities), which is why we still rely on a layered defense. That won’t change anytime soon.

Mike.

By Mike Rothman


Mike,

        Continuing the discussion of anti-explotation techniques, how do you view the effectiveness and efficiency of non-OS-based malware prevention mechanisms such as buffer overflow protection (by techniques such as stack protection) and kernel memory protection (e.g. through wrapping system calls)?

Thanks.

By Solution Marketing @ Lumension


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