Jailbroken iPhones leave users more vulnerable

Jailbreaking a handset may remove up to 80 percent of its security protections

Jailbreaking an iPhone leaves users vulnerable to attack by stripping away most of the handset's security protections, a security researcher warned Thursday.

"If you care about security, don't use a jailbroken iPhone," said security researcher Charlie Miller, speaking at the SyScan security conference in Singapore on Thursday.

[ Related: Apple patching serious SMS vulnerability on iPhone. | Read Tom Yager's eight easy steps to iPhone security. | Stay ahead of advances in mobile technology with InfoWorld's Mobile Edge blog and Mobilize newsletter. ]

"Jailbreaking" is a term used to describe the process of stripping away the protections that prevent a user from installing applications on an iPhone that have not been digitally signed by Apple. Jailbreaking tools have been popular among users in the United States and elsewhere who do not want to be tied to a specific operator, or who want to add software or capabilities to the phone that Apple doesn't offer.

The process removes around 80 percent of the security protections built into the phone's software, making it more vulnerable, Miller said.

Overall, the stripped-down version of Mac OS X used in the iPhone makes it more secure than computers running the full version of the operating system, Miller said.

Many capabilities contained in the full version of the operating system, like support for Java and Adobe Flash, are not available on the iPhone. In addition, the iPhone doesn't support many of the features contained in PDF files, which have proved to be a fertile source of Mac OS X vulnerabilities. This gives attackers fewer options when looking for vulnerabilities to exploit, he said.

In addition, iPhones are limited to running applications that have been digitally signed by Apple, which means that an attacker cannot simply install and run their own software on the handset. The iPhone also has hardware protections for data stored in memory.

Jailbreaking an iPhone disables these two security functions, making the phone more vulnerable to an attack, Miller said.

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