Entries Tagged "Bluetooth"

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Tracking People via Bluetooth on Their Phones

We’ve always known that phones—and the people carrying them—can be uniquely identified from their Bluetooth signatures, and that we need security techniques to prevent that. This new research shows that that’s not enough.

Computer scientists at the University of California San Diego proved in a study published May 24 that minute imperfections in phones caused during manufacturing create a unique Bluetooth beacon, one that establishes a digital signature or fingerprint distinct from any other device. Though phones’ Bluetooth uses cryptographic technology that limits trackability, using a radio receiver, these distortions in the Bluetooth signal can be discerned to track individual devices.

[…]

The study’s scientists conducted tests to show whether multiple phones being in one place could disrupt their ability to track individual signals. Results in an initial experiment showed they managed to discern individual signals for 40% of 162 devices in public. Another, scaled-up experiment showed they could discern 47% of 647 devices in a public hallway across two days.

The tracking range depends on device and the environment, and it could be several hundred feet, but in a crowded location it might only be 10 or so feet. Scientists were able to follow a volunteer’s signal as they went to and from their house. Certain environmental factors can disrupt a Bluetooth signal, including changes in environment temperature, and some devices send signals with more power and range than others.

One might say “well, I’ll just keep Bluetooth turned off when not in use,” but the researchers said they found that some devices, especially iPhones, don’t actually turn off Bluetooth unless a user goes directly into settings to turn off the signal. Most people might not even realize their Bluetooth is being constantly emitted by many smart devices.

Posted on June 17, 2022 at 6:06 AM • View Comments

Bluetooth Flaw Allows Remote Unlocking of Digital Locks

Locks that use Bluetooth Low Energy to authenticate keys are vulnerable to remote unlocking. The research focused on Teslas, but the exploit is generalizable.

In a video shared with Reuters, NCC Group researcher Sultan Qasim Khan was able to open and then drive a Tesla using a small relay device attached to a laptop which bridged a large gap between the Tesla and the Tesla owner’s phone.

“This proves that any product relying on a trusted BLE connection is vulnerable to attacks even from the other side of the world,” the UK-based firm said in a statement, referring to the Bluetooth Low Energy (BLE) protocol—technology used in millions of cars and smart locks which automatically open when in close proximity to an authorised device.

Although Khan demonstrated the hack on a 2021 Tesla Model Y, NCC Group said any smart locks using BLE technology, including residential smart locks, could be unlocked in the same way.

Another news article.

EDITED TO ADD (6/14): A longer version of the demo video.

Posted on May 20, 2022 at 6:02 AM • View Comments

iPhone Malware that Operates Even When the Phone Is Turned Off

Researchers have demonstrated iPhone malware that works even when the phone is fully shut down.

t turns out that the iPhone’s Bluetooth chip­—which is key to making features like Find My work­—has no mechanism for digitally signing or even encrypting the firmware it runs. Academics at Germany’s Technical University of Darmstadt figured out how to exploit this lack of hardening to run malicious firmware that allows the attacker to track the phone’s location or run new features when the device is turned off.

[…]

The research is the first—or at least among the first—to study the risk posed by chips running in low-power mode. Not to be confused with iOS’s low-power mode for conserving battery life, the low-power mode (LPM) in this research allows chips responsible for near-field communication, ultra wideband, and Bluetooth to run in a special mode that can remain on for 24 hours after a device is turned off.

The research is fascinating, but the attack isn’t really feasible. It requires a jailbroken phone, which is hard to pull off in an adversarial setting.

Slashdot thread.

Posted on May 18, 2022 at 6:06 AM • View Comments

Cheating on Tests

Interesting story of test-takers in India using Bluetooth-connected flip-flops to communicate with accomplices while taking a test.

What’s interesting is how this cheating was discovered. It’s not that someone noticed the communication devices. It’s that the proctors noticed that cheating test takers were acting hinky.

Posted on October 4, 2021 at 9:40 AM • View Comments

Tracking People by their MAC Addresses

Yet another article on the privacy risks of static MAC addresses and always-on Bluetooth connections. This one is about wireless headphones.

The good news is that product vendors are fixing this:

Several of the headphones which could be tracked over time are for sale in electronics stores, but according to two of the manufacturers NRK have spoken to, these models are being phased out.

“The products in your line-up, Elite Active 65t, Elite 65e and Evolve 75e, will be going out of production before long and newer versions have already been launched with randomized MAC addresses. We have a lot of focus on privacy by design and we continuously work with the available security measures on the market,” head of PR at Jabra, Claus Fonnesbech says.

“To run Bluetooth Classic we, and all other vendors, are required to have static addresses and you will find that in older products,” Fonnesbech says.

Jens Bjørnkjær Gamborg, head of communications at Bang & Olufsen, says that “this is products that were launched several years ago.”

“All products launched after 2019 randomize their MAC-addresses on a frequent basis as it has become the market standard to do so,” Gamborg says.

EDITED TO ADD (9/13): It’s not enough to randomly change MAC addresses. Any other plaintext identifiers need to be changed at the same time.

Posted on September 6, 2021 at 6:11 AM • View Comments

Security Analysis of Apple’s “Find My…” Protocol

Interesting research: “Who Can Find My Devices? Security and Privacy of Apple’s Crowd-Sourced Bluetooth Location Tracking System“:

Abstract: Overnight, Apple has turned its hundreds-of-million-device ecosystem into the world’s largest crowd-sourced location tracking network called offline finding (OF). OF leverages online finder devices to detect the presence of missing offline devices using Bluetooth and report an approximate location back to the owner via the Internet. While OF is not the first system of its kind, it is the first to commit to strong privacy goals. In particular, OF aims to ensure finder anonymity, untrackability of owner devices, and confidentiality of location reports. This paper presents the first comprehensive security and privacy analysis of OF. To this end, we recover the specifications of the closed-source OF protocols by means of reverse engineering. We experimentally show that unauthorized access to the location reports allows for accurate device tracking and retrieving a user’s top locations with an error in the order of 10 meters in urban areas. While we find that OF’s design achieves its privacy goals, we discover two distinct design and implementation flaws that can lead to a location correlation attack and unauthorized access to the location history of the past seven days, which could deanonymize users. Apple has partially addressed the issues following our responsible disclosure. Finally, we make our research artifacts publicly available.

There is also code available on GitHub, which allows arbitrary Bluetooth devices to be tracked via Apple’s Find My network.

Posted on March 15, 2021 at 6:16 AM • View Comments

New Bluetooth Vulnerability

There’s a new unpatched Bluetooth vulnerability:

The issue is with a protocol called Cross-Transport Key Derivation (or CTKD, for short). When, say, an iPhone is getting ready to pair up with Bluetooth-powered device, CTKD’s role is to set up two separate authentication keys for that phone: one for a “Bluetooth Low Energy” device, and one for a device using what’s known as the “Basic Rate/Enhanced Data Rate” standard. Different devices require different amounts of data—and battery power—from a phone. Being able to toggle between the standards needed for Bluetooth devices that take a ton of data (like a Chromecast), and those that require a bit less (like a smartwatch) is more efficient. Incidentally, it might also be less secure.

According to the researchers, if a phone supports both of those standards but doesn’t require some sort of authentication or permission on the user’s end, a hackery sort who’s within Bluetooth range can use its CTKD connection to derive its own competing key. With that connection, according to the researchers, this sort of erzatz authentication can also allow bad actors to weaken the encryption that these keys use in the first place—which can open its owner up to more attacks further down the road, or perform “man in the middle” style attacks that snoop on unprotected data being sent by the phone’s apps and services.

Another article:

Patches are not immediately available at the time of writing. The only way to protect against BLURtooth attacks is to control the environment in which Bluetooth devices are paired, in order to prevent man-in-the-middle attacks, or pairings with rogue devices carried out via social engineering (tricking the human operator).

However, patches are expected to be available at one point. When they’ll be, they’ll most likely be integrated as firmware or operating system updates for Bluetooth capable devices.

The timeline for these updates is, for the moment, unclear, as device vendors and OS makers usually work on different timelines, and some may not prioritize security patches as others. The number of vulnerable devices is also unclear and hard to quantify.

Many Bluetooth devices can’t be patched.

Final note: this seems to be another example of simultaneous discovery:

According to the Bluetooth SIG, the BLURtooth attack was discovered independently by two groups of academics from the École Polytechnique Fédérale de Lausanne (EPFL) and Purdue University.

Posted on September 17, 2020 at 6:18 AM • View Comments

Bluetooth Vulnerability: BIAS

This is new research on a Bluetooth vulnerability (called BIAS) that allows someone to impersonate a trusted device:

Abstract: Bluetooth (BR/EDR) is a pervasive technology for wireless communication used by billions of devices. The Bluetooth standard includes a legacy authentication procedure and a secure authentication procedure, allowing devices to authenticate to each other using a long term key. Those procedures are used during pairing and secure connection establishment to prevent impersonation attacks. In this paper, we show that the Bluetooth specification contains vulnerabilities enabling to perform impersonation attacks during secure connection establishment. Such vulnerabilities include the lack of mandatory mutual authentication, overly permissive role switching, and an authentication procedure downgrade. We describe each vulnerability in detail, and we exploit them to design, implement, and evaluate master and slave impersonation attacks on both the legacy authentication procedure and the secure authentication procedure. We refer to our attacks as Bluetooth Impersonation AttackS (BIAS).

Our attacks are standard compliant, and are therefore effective against any standard compliant Bluetooth device regardless the Bluetooth version, the security mode (e.g., Secure Connections), the device manufacturer, and the implementation details. Our attacks are stealthy because the Bluetooth standard does not require to notify end users about the outcome of an authentication procedure, or the lack of mutual authentication. To confirm that the BIAS attacks are practical, we successfully conduct them against 31 Bluetooth devices (28 unique Bluetooth chips) from major hardware and software vendors, implementing all the major Bluetooth versions, including Apple, Qualcomm, Intel, Cypress, Broadcom, Samsung, and CSR.

News articles.

Posted on May 26, 2020 at 6:54 AM • View Comments

Me on COVID-19 Contact Tracing Apps

I was quoted in BuzzFeed:

“My problem with contact tracing apps is that they have absolutely no value,” Bruce Schneier, a privacy expert and fellow at the Berkman Klein Center for Internet & Society at Harvard University, told BuzzFeed News. “I’m not even talking about the privacy concerns, I mean the efficacy. Does anybody think this will do something useful? … This is just something governments want to do for the hell of it. To me, it’s just techies doing techie things because they don’t know what else to do.”

I haven’t blogged about this because I thought it was obvious. But from the tweets and emails I have received, it seems not.

This is a classic identification problem, and efficacy depends on two things: false positives and false negatives.

  • False positives: Any app will have a precise definition of a contact: let’s say it’s less than six feet for more than ten minutes. The false positive rate is the percentage of contacts that don’t result in transmissions. This will be because of several reasons. One, the app’s location and proximity systems—based on GPS and Bluetooth—just aren’t accurate enough to capture every contact. Two, the app won’t be aware of any extenuating circumstances, like walls or partitions. And three, not every contact results in transmission; the disease has some transmission rate that’s less than 100% (and I don’t know what that is).
  • False negatives: This is the rate the app fails to register a contact when an infection occurs. This also will be because of several reasons. One, errors in the app’s location and proximity systems. Two, transmissions that occur from people who don’t have the app (even Singapore didn’t get above a 20% adoption rate for the app). And three, not every transmission is a result of that precisely defined contact—the virus sometimes travels further.

Assume you take the app out grocery shopping with you and it subsequently alerts you of a contact. What should you do? It’s not accurate enough for you to quarantine yourself for two weeks. And without ubiquitous, cheap, fast, and accurate testing, you can’t confirm the app’s diagnosis. So the alert is useless.

Similarly, assume you take the app out grocery shopping and it doesn’t alert you of any contact. Are you in the clear? No, you’re not. You actually have no idea if you’ve been infected.

The end result is an app that doesn’t work. People will post their bad experiences on social media, and people will read those posts and realize that the app is not to be trusted. That loss of trust is even worse than having no app at all.

It has nothing to do with privacy concerns. The idea that contact tracing can be done with an app, and not human health professionals, is just plain dumb.

EDITED TO ADD: This Brookings essay makes much the same point.

EDITED TO ADD: This post has been translated into Spanish.

Posted on May 1, 2020 at 6:22 AM • View Comments

Major Bluetooth Vulnerability

Bluetooth has a serious security vulnerability:

In some implementations, the elliptic curve parameters are not all validated by the cryptographic algorithm implementation, which may allow a remote attacker within wireless range to inject an invalid public key to determine the session key with high probability. Such an attacker can then passively intercept and decrypt all device messages, and/or forge and inject malicious messages.

Paper. Website. Three news articles.

This is serious. Update your software now, and try not to think about all of the Bluetooth applications that can’t be updated.

Posted on July 25, 2018 at 2:08 PM • View Comments

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Sidebar photo of Bruce Schneier by Joe MacInnis.