Custom Features Incur Security Flaws In Popular Android Smartphones

It's not the Android app stores that you need to worry most about: The biggest security weaknesses in most Android smartphones today are the custom apps and features that come packaged with the devices, new research shows.

Those are some of the findings from researchers at NC State who recently studied how custom vendor features on Android smartphones affect the security of the devices. Some 60 percent of all vulnerabilities the researchers found in popular smartphone models were due to what the researchers call "vendor customizations," or features the smartphone manufacturers tweak or include with the phones.

Another shocker: Newer smartphone models aren't necessarily more secure, according to NC State researchers Lei Wu, Michael Grace, Yajin Zhou, Chiachih Wu, and Xuxian Jiang, who will present their research tomorrow at the ACM Conference on Computer and Communications Security in Berlin.

"We all know that Android, though popular, has one major problem: fragmentation. Among other [things], vendor customizations play a key role in contributing to the fragmentation," Jiang said in an email interview. "We are interested in better understanding how vendor customizations will impact overall Android security."

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Jiang and his team studied Android Version 2.X and Version 4.X models from Samsung, HTC, LG, Sony, and Google -- specifically, the Samsung Galaxy S2 and S3; the HTC Wildfire S and One X; the LG Optimus P350 and Optimus P880; Sony Xperia Arc S and Xperia SL; and the Google Nexus S and Nexus 4. Some 80 percent of the apps on those phones were preloaded and customized by the smartphone manufacturers; all 10 devices were vulnerable due to those preloaded apps.

Jiang said the team's research uncovered other surprising trends: On average, 85 percent of all of these preloaded apps have too many user privileges on the devices, thanks to vendor customization. That means an app gets permissions it wouldn't actually use, such as the ability to send SMS messages, record audio, or make phone calls without the user's permission, for example.

The Android Version 2.x phones each contained an average of 22.4 vulnerabilities; the newer Version 4.x phones, an average of 18.4 vulnerabilities.

Upgrading to the newest smartphone model doesn't necessarily help securitywise, the researchers found. Every time the vendor customizes more features on the phone, it opens the door for more security flaws. "While a newer Android phone may run a newer version of OS , which might already fix vulnerabilities present in older versions, vendor customizations, however, being significant on these devices, could still introduce additional vulnerabilities into newer phones," Jiang said.

Of the Android 4.x phones, the Google Nexus 4 performed the best, with just three total vulnerabilities, and the Galaxy S3 fared worst, with 40 total bugs. That was only a slight improvement overall from the Android 3.x phones, however, where the Google Nexus S and the Sony Xperia Arc each had eight flaws (the lowest), the HTC Wildfire S had 40 flaws, and the Samsung Galaxy S2, 39.

Buyers can't do much about these preloaded apps, Jiang said, but smartphone manufacturers can step up by taking security and privacy more seriously in their designs. He said they should adopt the least-privilege principle when building apps and conduct white- and black-box vulnerability analysis to find and fix bugs.

"Through this study, we hope to highlight the need for heightened focus on security by the smartphone industry. And the work was supported in part by the U.S. National Science Foundation," Jiang says.

The full NC State research paper, titled "The Impact of Vendor Customizations on Android Security," is available here (PDF) for download.

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