Apple has released a set of updates to its operating system across its range of hardware, from the Apple Watch to the Mac. While the updates cover a number of issues, a USB attack and its prevention may be the most important among them.

The mass release isn't unusual behavior for Apple, says Thomas Reed, director of Mac and mobile at Malwarebytes Labs. "When Apple releases these updates, they tend to release one for each of their products," Reed says. "They'll release a whole bunch of these on the same date."

Apparent from an inspection of the issues addressed in the MacOS update is that companies continue to deal with fallout from the Meltdown and Spectre vulnerabilities. On the website announcing the updates, Apple describes one vulnerability in which " ... one process may infer register values of other processes through a speculative execution side channel that infers their value." This could be the broad description of the entire family of Meltdown vulnerabilities.

Reed describes most of the remaining updates as important but not particularly unusual. One, though, has seen a great deal of attention from analysts and law enforcement officials: USB Restricted Mode.

USB Restricted Mode is a new feature that prevents data from being downloaded from an iOS device unless the device has been unlocked within the past hour. The new restriction seems targeted against devices like the GreyLock, which law enforcement agencies have purchased and used to conduct forensic analysis on iPhones and iPads.

"Companies don't want to make things harder specifically for law enforcement, but we've seen these devices being used by bad actors or bad governments," Reed says. At the same time, he notes a limitation in the restriction: "I don't understand why they didn't just make it so you have to unlock the device every time, rather than having the one-hour limit."

That one-hour window in which data can be downloaded from the device has been seized on by analysts and journalists as a significant flaw in the protection. Oleg Afonin, who blogs at Elcomsoft.com, explains that plugging an accessory (just about any accessory, at that) into the Lightning jack during the one-hour window can easily extend the window of vulnerability indefinitely.

While Afonin's tests showed that USB Restricted Mode operates as planned in most cases – holding the ports closed through reboots and protecting the device from unauthorized data exfiltration – the ability to work around the mode with a simple accessory is a critical weakness.

Even with this limitation, Reed says that applying the updates and patches is critical for the security of all affected Apple devices. "The more important thing for people to know about the updates is just how important it is to install them," he says. And the reason is one of the paradoxical qualities of software patching.

"Just as soon as they're out there, the information on what was patched is published, and hackers have a clue about how they could hack people with the older systems," Reed explains. "It's almost like the update makes the older systems even more vulnerable."

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