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Mobile Devices, Your Network, and Passive Sniffing

Do you know how many mobile devices reside on your network? Is your security architecture designed to secure the mobile platform and protect your users and the network from the threats they pose?

Stack of Cell Phones

Mobile devices are a security concern for many reasons. Mobile devices are typically unmanaged – meaning they may or may not be running AV software, a firewall, or conform to enforceable security policies. Yet, whether they are provided to your employees as part of your operations or not, they are likely accessing resources on your network. To compound the problem, many mobile devices connect to your local network and the Internet directly on two separate mediums. For example, the device may associate to a wireless belonging to your organization and a 3G/4G connection to the Internet.

In this scenario, there is a risk of data leaving your organization through a personal device—which may not have received the same security checks and patches as corporate-issued tools. Software running on mobile devices may violate an organization’s policy on appropriate network usage.

It is difficult to manage or assess mobile risk without knowing which devices are being used, where they are located on the network, and to what extent they are deployed. To this end, Tenable’s Passive Vulnerability Scanner (PVS) now contains a new set of plugins that detects where mobile devices are connecting to your internal IP space and allows you to detect vulnerabilities by sniffing the network traffic.

PVS plugins 4134, 5287, and 6067-6086 are dedicated to logging mobile devices and finding, where possible, the software/hardware version information of the devices. There is also a new plugin category called "Mobile Devices" in PVS that allows you to easily sort the data that has been collected. Devices that PVS can detect include tablets, mobile phones, e-book readers, and more.

Once you have found a mobile device, you can easily see what sort of traffic they have been passing or accessing on your network. For example, I've created the following filter in SecurityCenter:

SecurityCenter PVSFilter

The results of the filter showed the mobile devices in use at this facility:

SC / PVS Mobile Device Summry

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You can then run a report to retrieve an IP summary of all mobile devices to see what else SecurityCenter may know about these devices, such as their names or MAC addresses:

SC / PVS Mobile IP Summary

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In this case, an iPhone/iPad was detected on the network:

SC / PVS iPad Summary

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This query reveals all of the vulnerabilities discovered on the device-- actively discovered with Nessus and passively discovered with PVS as traffic to and from the device was observed on the network. The iPhone/iPad in question is not up-to-date on the latest patches.


Monitoring mobile devices on your network can provide interesting and actionable results. For example, Apple iPhone and iPad users must connect their device to a computer in order to upgrade from iOS version 4 to version 5. It wasn't until iOS 5.1 that Apple introduced over-the-air-updates. Using the tools and methods described above, you can seek out devices that need to be upgraded. PVS can also detect applications running on the devices, for example you can see which devices are running Angry Birds, based on the connections made by the apps to servers on the Internet. This means you can see who isn't applying updates, and who has which applications installed on their phones.

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