How NSO Group’s zero-click iPhone-Hacking Exploit Works

[…] researchers managed to technically deconstruct just how one of the company’s notorious “zero-click” attacks work. Indeed, researchers with Google’s Project Zero published a detailed break-down that shows how an NSO exploit, dubbed “FORCEDENTRY,” can swiftly and silently take over a phone.

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Initial details about it were captured by Citizen Lab, a research unit at the University of Toronto that has frequently published research related to NSO’s activities. Citizen Lab researchers managed to get ahold of phones that had been subjected to the company’s “zero-click” attacks and, in September, published initial research about how they worked. Around the same time, Apple announced it was suing NSO and also published security updates to patch the problems associated with the exploit.

Citizen Lab ultimately shared its findings with Google’s researchers who, as of last week, finally published their analysis of the attacks. As you might expect, it’s pretty incredible—and frightening—stuff.

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Probably the most terrifying thing about FORCEDENTRY is that, according to Google’s researchers, the only thing necessary to hack a person was their phone number or their AppleID username.

Using one of those identifiers, the wielder of NSO’s exploit could quite easily compromise any device they wished. The attack process was simple: What appeared to be a GIF was texted to the victim’s phone via iMessage. However, the image in question was not actually a GIF; instead, it was a malicious PDF that had been dressed up with a .gif extension. Within the file was a highly sophisticated malicious payload that could hijack a vulnerability in Apple’s image processing software and use it to quickly take over valuable resources within the targeted device.

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what FORCEDENTRY did was exploit a zero-day vulnerability within Apple’s image rendering library, CoreGraphics—the software that iOS uses to process on-device imagery and media. That vulnerability, officially tracked as CVE-2021-30860, is associated with an old piece of free, open-source code that iOS was apparently leveraging to encode and decode PDF files—the Xpdf implementation of JBIG2.

Here’s where the attack gets really wild, though. By exploiting the image processing vulnerability, FORCEDENTRY was able to get inside the targeted device and use the phone’s own memory to build a rudimentary virtual machine, basically a “computer within a computer.” From there, the machine could “bootstrap” NSO’s Pegasus malware from within, ultimately relaying data back to whoever had deployed the exploit.

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The vulnerability related to this exploit was fixed in Apple’s iOS 14.8 update (issued in September), though some computer researchers have warned that if a person’s phone was compromised by Pegasus prior to the update, a patch may not do all that much to keep intruders out.

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Source: How NSO Group’s iPhone-Hacking Exploit Works

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