When you think about how hackers could break into your smartphone, you probably start with clicking a malicious link in a text, downloading a fraudulent app, or some other way you accidentally let them in. It turns out that’s not necessarily so—not even on the iPhone, where simply receiving an iMessage could be enough to get yourself hacked.
At the Black Hat security conference in Las Vegas on Wednesday, Google Project Zero researcher Natalie Silvanovich is presenting multiple so-called “interaction-less” bugs in Apple’s iOS iMessage client that could be exploited to gain control of a user’s device. And while Apple has already patched five of them, a few have yet to be patched.
“These can be turned into the sort of bugs that will execute code and be able to eventually be used for weaponized things like accessing your data,” Silvanovich says. “So the worst-case scenario is that these bugs are used to harm users.”
Lily Hay Newman covers information security, digital privacy, and hacking for WIRED.
Silvanovich, who worked on the research with fellow Project Zero member Samuel Groß, got interested in interaction-less bugs because of a recent, dramatic WhatsApp vulnerability that allowed nation-state spies to compromise a phone just by calling it—even if the recipient didn’t answer the call.
But when she looked for similar issues in SMS, MMS, and visual voicemail, she came up empty. Silvanovich had assumed that iMessage would be a more scrutinized and locked down target, but when she started reverse-engineering and looking for flaws, she quickly found multiple exploitable bugs.
This may be because iMessage is such a complex platform that offers an array of communication options and features. It encompasses Animojis, rendering files like photos and videos, and integration with other apps—everything from Apple Pay and iTunes to Fandango and Airbnb. All of these extensions and interconnections make mistakes and weaknesses more likely.
One of the most interesting interaction-less bugs Silvanovich found was a fundamental logic issue that could have allowed a hacker to easily extract data from a user’s messages. An attacker could send a specially crafted text message to a target, and the iMessage server would send specific user data back, like the content of their SMS messages or images. The victim wouldn’t even have to open their iMessage app for the attack to work. iOS has protections in place that would usually block an attack like this, but because it takes advantage of the system’s underlying logic, iOS’s defenses interpret it as legitimate and intended.
Other bugs Silvanovich found could lead to malicious code being placed on a victim’s device, again from just an incoming text.
Interaction-less iOS bugs are highly coveted by exploit vendors and nation-state hackers, because they make it so easy to compromise a target’s device without requiring any buy-in from the victim. The six vulnerabilities Silvanovich found—with more yet to be announced—would potentially be worth millions or even tens of millions of dollars on the exploit market.
“Bugs like this haven’t been made public for a long time,” Silvanovich says. “There’s a lot of additional attack surface in programs like iMessage. The individual bugs are reasonably easy to patch, but you can never find all the bugs in software, and every library you use will become an attack surface. So that design problem is relatively difficult to fix.”
Silvanovich emphasizes that the security of iMessage is strong overall, and that Apple is far from the only developer that sometimes make mistakes in grappling with this conceptual issue. Apple did not return a request from WIRED for comment.
“It doesn’t matter how good your crypto is if the program has bugs on the receiving end.”
Natalie Silvanovich, Google Project Zero
Silvanovich says she also looked for interaction-less bugs in Android, but hasn’t found any so far. She notes, though, that it’s likely that such vulnerabilities exist in almost any target. Over the past year she’s found similar flaws in WhatsApp, FaceTime, and the video conferencing protocol webRTC.
“Maybe this is an area that gets missed in security,” Silvanovich says. “There’s a huge amount of focus on implementation of protections like cryptography, but it doesn’t matter how good your crypto is if the program has bugs on the receiving end.”
The best thing you can do to protect yourself against interaction-less attacks is keep your phone operating system and apps updated; Apple patched all six of the iMessage bugs Silvanovich is presenting in the recently released iOS 12.4, and in macOS 10.14.6. But beyond that, it’s up to developers to avoid introducing these types of bugs in their code, or spot them as quickly as possible. Given how inexorable interaction-less attacks can be, there’s not a lot users can do to stop them once malicious messages or calls start pouring in.