Storming a castle's walls isn't always the best way to bring them down. Sometimes less direct siege methods work better, as a trio of researchers discovered when launching an attack on the walled garden Apple's built around its iPhone.
The Georgia Tech researchers demonstrated at the Black Hat security conference in Las Vegas this week a method for using a home-brewed charger to substitute an infected version of Facebook's iPhone app for the legitimate software with no one being the wiser.
For Apple, the demo is the second time in recent weeks that cracks have begun to show in the company's "walled garden" around its mobile ecosystem. A week ago, a website the company runs for its developers was penetrated by a Turkish security researcher and some 100,000 member records removed from the site.
"A walled garden is just that: a wall," Tom Kellermann, vice president of cyber security for Trend Micro, said via email. "The method employed demonstrates a technique to tunnel under that wall."
Because the vulnerability discovered by the researchers involves a hardware flaw, it could present a difficult security challenge for Apple, Kellermann said. But since the tactic only works on a one-to-one basis, the attack isn't very scalable.
"Apple's greatest vulnerability still lies in attacks targeting apps and websites running in Safari," Kellermann added.
Choosing Apple, considered a very secure ecosystem, as a target for their demonstration made the attack more fascinating, said Alex Watson, director of security research at Websense.
The level of detail in the demo also impressed Watson. "It wasn't just a proof of concept saying, 'This is possible,'" he said in an interview. "They were able to very surreptitiously delete a Facebook application and put a compromised Facebook application in the exact same spot on the screen where the previous one existed.
"It shows a very convincing and very repeatable attack that would very hard to detect," he added.
To attack an iPhone 5, the researchers — Billy Lau and graduate students Yeongjin Jang and Chengyu Song — built a bogus charger based on a $45 single-board computer called a BeagleBoard. The box — dubbed Mactan, the scientific name for the Black Widow spider — exploits code in the operating system that allows anyone with a developer's license to install custom software on the handset.
Once connected to the phone, Mactan reads the handset's Unique Device Identifier, registers it as a developer's test device and then uses those privileges to install malware.
The compromised Facebook app contained a Trojan that could capture screenshots and button touches and send them to a server connected to the Internet.
The researchers were not immediately available for comment.
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