Corporate security. As noted, the iPad Mini has the same strong enterprise-class capabilities as any iOS device, including a highly compatible VPN client. Also as noted, the Nexus 7 has the moderate security capabilities of most recent Android tablets. The Nexus 7 has Android's standard VPN support, which unfortunately does not include Cisco IPSec VPNs (you'll need to download Cisco's AnyConnect client as well as buy a client access license for it). The Kindle Fire HD provides the basics of Exchange device security, including encryption, and there are even a few VPN vendors' clients for it in the Amazon Appstore -- but not for Cisco VPNs.
Note that both the Nexus 7 and Kindle Fire HD, like all Android 3 and 4 devices, come unencrypted. The encryption process requires a full charge, so you can't do it as soon as you open the box, and takes about 30 to 45 minutes. Note that you can't enable encryption on the Kindle Fire HD in its Settings app; only when you try to connect to an Exchange server that requires encryption are you given the ability to turn on encryption. If you're on the road without a full battery charge the first time you try to connect to Exchange, you'll be out of luck. Like all iOS devices, the iPad Mini is always encrypted, and encryption can't be disabled.
All three media tablets support passwords, so you can prevent unauthorized people from using them.
Family security. But there's another kind of security to consider for a media tablet since it's likely to be shared by several family members. In this regard, the Kindle Fire HD is the most secure, thanks to its FreeTime app that lets you set up separate content libraries for each person, essentially giving them a separate login to just their library. Parents can use that capability to restrict what their kids can access, as well as limit the number of hours of usage each day.
The iPad Mini's Guided Access lets you restrict the tablet to a specific app and even block some of an app's capabilities (such as Buy buttons) by drawing blocking ovals around their controls. But this new iOS 6 feature has to be enabled each time you want to use it and can be used for just one app at a time. It's fine when you want to hand your iPad to your kid for a specific purpose, but it's nowhere near as useful as the ability to set up separate environments, as the Kindle Fire HD can.
The iPad has a comprehensive set of parental controls that let you configure what your kids can access. Tech-savvy parents can even use Apple's free Apple Configurator tool for OS X to create and deploy profiles with such configurations to their kids' devices, as well as update them remotely (though we're talking supergeek parents here). Safari's private browsing mode lets parents access Web pages they don't want their kids to easily see, as this mode ensures no history is kept of the visited pages.
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