Tag Archives: smartphones

Using Machine Learning to Detect Keystrokes

Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2023/08/using-machine-learning-to-detect-keystrokes.html

Researchers have trained a ML model to detect keystrokes by sound with 95% accuracy.

“A Practical Deep Learning-Based Acoustic Side Channel Attack on Keyboards”

Abstract: With recent developments in deep learning, the ubiquity of microphones and the rise in online services via personal devices, acoustic side channel attacks present a greater threat to keyboards than ever. This paper presents a practical implementation of a state-of-the-art deep learning model in order to classify laptop keystrokes, using a smartphone integrated microphone. When trained on keystrokes recorded by a nearby phone, the classifier achieved an accuracy of 95%, the highest accuracy seen without the use of a language model. When trained on keystrokes recorded using the video-conferencing software Zoom, an accuracy of 93% was achieved, a new best for the medium. Our results prove the practicality of these side channel attacks via off-the-shelf equipment and algorithms. We discuss a series of mitigation methods to protect users against these series of attacks.

News article.

Brute-Forcing a Fingerprint Reader

Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2023/05/brute-forcing-a-fingerprint-reader.html

It’s neither hard nor expensive:

Unlike password authentication, which requires a direct match between what is inputted and what’s stored in a database, fingerprint authentication determines a match using a reference threshold. As a result, a successful fingerprint brute-force attack requires only that an inputted image provides an acceptable approximation of an image in the fingerprint database. BrutePrint manipulates the false acceptance rate (FAR) to increase the threshold so fewer approximate images are accepted.

BrutePrint acts as an adversary in the middle between the fingerprint sensor and the trusted execution environment and exploits vulnerabilities that allow for unlimited guesses.

In a BrutePrint attack, the adversary removes the back cover of the device and attaches the $15 circuit board that has the fingerprint database loaded in the flash storage. The adversary then must convert the database into a fingerprint dictionary that’s formatted to work with the specific sensor used by the targeted phone. The process uses a neural-style transfer when converting the database into the usable dictionary. This process increases the chances of a match.

With the fingerprint dictionary in place, the adversary device is now in a position to input each entry into the targeted phone. Normally, a protection known as attempt limiting effectively locks a phone after a set number of failed login attempts are reached. BrutePrint can fully bypass this limit in the eight tested Android models, meaning the adversary device can try an infinite number of guesses. (On the two iPhones, the attack can expand the number of guesses to 15, three times higher than the five permitted.)

The bypasses result from exploiting what the researchers said are two zero-day vulnerabilities in the smartphone fingerprint authentication framework of virtually all smartphones. The vulnerabilities—­one known as CAMF (cancel-after-match fail) and the other MAL (match-after-lock)—result from logic bugs in the authentication framework. CAMF exploits invalidate the checksum of transmitted fingerprint data, and MAL exploits infer matching results through side-channel attacks.

Depending on the model, the attack takes between 40 minutes and 14 hours.


The ability of BrutePrint to successfully hijack fingerprints stored on Android devices but not iPhones is the result of one simple design difference: iOS encrypts the data, and Android does not.

Other news articles. Research paper.

FBI Advising People to Avoid Public Charging Stations

Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2023/04/fbi-advising-people-to-avoid-public-charging-stations.html

The FBI is warning people against using public phone-charging stations, worrying that the combination power-data port can be used to inject malware onto the devices:

Avoid using free charging stations in airports, hotels, or shopping centers. Bad actors have figured out ways to use public USB ports to introduce malware and monitoring software onto devices that access these ports. Carry your own charger and USB cord and use an electrical outlet instead.

How much of a risk is this, really? I am unconvinced, although I do carry a USB condom for charging stations I find suspicious.

News article.

Recovering Smartphone Voice from the Accelerometer

Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2022/12/recovering-smartphone-voice-from-the-accelerometer.html

Yet another smartphone side-channel attack: “EarSpy: Spying Caller Speech and Identity through Tiny Vibrations of Smartphone Ear Speakers“:

Abstract: Eavesdropping from the user’s smartphone is a well-known threat to the user’s safety and privacy. Existing studies show that loudspeaker reverberation can inject speech into motion sensor readings, leading to speech eavesdropping. While more devastating attacks on ear speakers, which produce much smaller scale vibrations, were believed impossible to eavesdrop with zero-permission motion sensors. In this work, we revisit this important line of reach. We explore recent trends in smartphone manufacturers that include extra/powerful speakers in place of small ear speakers, and demonstrate the feasibility of using motion sensors to capture such tiny speech vibrations. We investigate the impacts of these new ear speakers on built-in motion sensors and examine the potential to elicit private speech information from the minute vibrations. Our designed system EarSpy can successfully detect word regions, time, and frequency domain features and generate a spectrogram for each word region. We train and test the extracted data using classical machine learning algorithms and convolutional neural networks. We found up to 98.66% accuracy in gender detection, 92.6% detection in speaker detection, and 56.42% detection in digit detection (which is 5X more significant than the random selection (10%)). Our result unveils the potential threat of eavesdropping on phone conversations from ear speakers using motion sensors.

It’s not great, but it’s an impressive start.

Ukraine Intercepting Russian Soldiers’ Cell Phone Calls

Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2022/12/ukraine-intercepting-russian-soldiers-cell-phone-calls.html

They’re using commercial phones, which go through the Ukrainian telecom network:

“You still have a lot of soldiers bringing cellphones to the frontline who want to talk to their families and they are either being intercepted as they go through a Ukrainian telecommunications provider or intercepted over the air,” said Alperovitch. “That doesn’t pose too much difficulty for the Ukrainian security services.”


“Security has always been a mess, both in the army and among defence officials,” the source said. “For example, in 2013 they tried to get all the staff at the ministry of defence to replace our iPhones with Russian-made Yoto smartphones.

“But everyone just kept using the iPhone as a second mobile because it was much better. We would just keep the iPhone in the car’s glove compartment for when we got back from work. In the end, the ministry gave up and stopped caring. If the top doesn’t take security very seriously, how can you expect any discipline in the regular army?”

This isn’t a new problem and it isn’t a Russian problem. Here’s a more general article on the problem from 2020.

Russian Software Company Pretending to Be American

Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2022/11/russian-software-company-pretending-to-be-american.html

Computer code developed by a company called Pushwoosh is in about 8,000 Apple and Google smartphone apps. The company pretends to be American when it is actually Russian.

According to company documents publicly filed in Russia and reviewed by Reuters, Pushwoosh is headquartered in the Siberian town of Novosibirsk, where it is registered as a software company that also carries out data processing. It employs around 40 people and reported revenue of 143,270,000 rubles ($2.4 mln) last year. Pushwoosh is registered with the Russian government to pay taxes in Russia.

On social media and in US regulatory filings, however, it presents itself as a US company, based at various times in California, Maryland, and Washington, DC, Reuters found.

What does the code do? Spy on people:

Pushwoosh provides code and data processing support for software developers, enabling them to profile the online activity of smartphone app users and send tailor-made push notifications from Pushwoosh servers.

On its website, Pushwoosh says it does not collect sensitive information, and Reuters found no evidence Pushwoosh mishandled user data. Russian authorities, however, have compelled local companies to hand over user data to domestic security agencies.

I have called supply chain security “an insurmountably hard problem,” and this is just another example of that.

Another Event-Related Spyware App

Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2022/11/another-event-related-spyware-app.html

Last month, we were warned not to install Qatar’s World Cup app because it was spyware. This month, it’s Egypt’s COP27 Summit app:

The app is being promoted as a tool to help attendees navigate the event. But it risks giving the Egyptian government permission to read users’ emails and messages. Even messages shared via encrypted services like WhatsApp are vulnerable, according to POLITICO’s technical review of the application, and two of the outside experts.

The app also provides Egypt’s Ministry of Communications and Information Technology, which created it, with other so-called backdoor privileges, or the ability to scan people’s devices.

On smartphones running Google’s Android software, it has permission to potentially listen into users’ conversations via the app, even when the device is in sleep mode, according to the three experts and POLITICO’s separate analysis. It can also track people’s locations via smartphone’s built-in GPS and Wi-Fi technologies, according to two of the analysts.

Credit Card Fraud That Bypasses 2FA

Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2022/09/credit-card-fraud-that-bypasses-2fa.html

Someone in the UK is stealing smartphones and credit cards from people who have stored them in gym lockers, and is using the two items in combination to commit fraud:

Phones, of course, can be made inaccessible with the use of passwords and face or fingerprint unlocking. And bank cards can be stopped.

But the thief has a method which circumnavigates those basic safety protocols.

Once they have the phone and the card, they register the card on the relevant bank’s app on their own phone or computer. Since it is the first time that card will have been used on the new device, a one-off security passcode is demanded.

That verification passcode is sent by the bank to the stolen phone. The code flashes up on the locked screen of the stolen phone, leaving the thief to tap it into their own device. Once accepted, they have control of the bank account. They can transfer money or buy goods, or change access to the account.

Smartphones and Civilians in Wartime

Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2022/06/smartphones-and-civilians-in-wartime.html

Interesting article about civilians using smartphones to assist their militaries in wartime, and how that blurs the important legal distinction between combatants and non-combatants:

The principle of distinction between the two roles is a critical cornerstone of international humanitarian law­—the law of armed conflict, codified by decades of customs and laws such as the Geneva Conventions. Those considered civilians and civilian targets are not to be attacked by military forces; as they are not combatants, they should be spared. At the same time, they also should not act as combatants—­if they do, they may lose this status.

The conundrum, then, is how to classify a civilian who, with the use of their smartphone, potentially becomes an active participant in a military sensor system. (To be clear, solely having the app installed is not sufficient to lose the protected status. What matters is actual usage.) The Additional Protocol I to Geneva Conventions states that civilians enjoy protection from the “dangers arising from military operations unless and for such time as they take a direct part in hostilities.” Legally, if civilians engage in military activity, such as taking part in hostilities by using weapons, they forfeit their protected status, “for such time as they take a direct part in hostilities” that “affect[s] the military operations,” according to the International Committee of the Red Cross, the traditional impartial custodian of International Humanitarian Law. This is the case even if the people in question are not formally members of the armed forces. By losing the status of a civilian, one may become a legitimate military objective, carrying the risk of being directly attacked by military forces.

Using Pupil Reflection in Smartphone Camera Selfies

Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2022/05/using-pupil-reflection-in-smartphone-camera-selfies.html

Researchers are using the reflection of the smartphone in the pupils of faces taken as selfies to infer information about how the phone is being used:

For now, the research is focusing on six different ways a user can hold a device like a smartphone: with both hands, just the left, or just the right in portrait mode, and the same options in horizontal mode.

It’s not a lot of information, but it’s a start. (It’ll be a while before we can reproduce these results from Blade Runner.)

Research paper.

Samsung Encryption Flaw

Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2022/03/samsung-encryption-flaw.html

Researchers have found a major encryption flaw in 100 million Samsung Galaxy phones.

From the abstract:

In this work, we expose the cryptographic design and implementation of Android’s Hardware-Backed Keystore in Samsung’s Galaxy S8, S9, S10, S20, and S21 flagship devices. We reversed-engineered and provide a detailed description of the cryptographic design and code structure, and we unveil severe design flaws. We present an IV reuse attack on AES-GCM that allows an attacker to extract hardware-protected key material, and a downgrade attack that makes even the latest Samsung devices vulnerable to the IV reuse attack. We demonstrate working key extraction attacks on the latest devices. We also show the implications of our attacks on two higher-level cryptographic protocols between the TrustZone and a remote server: we demonstrate a working FIDO2 WebAuthn login bypass and a compromise of Google’s Secure Key Import.

Here are the details:

As we discussed in Section 3, the wrapping key used to encrypt the key blobs (HDK) is derived using a salt value computed by the Keymaster TA. In v15 and v20-s9 blobs, the salt is a deterministic function that depends only on the application ID and application data (and constant strings), which the Normal World client fully controls. This means that for a given application, all key blobs will be encrypted using the same key. As the blobs are encrypted in AES-GCM mode-of-operation, the security of the resulting encryption scheme depends on its IV values never being reused.

Gadzooks. That’s a really embarrassing mistake. GSM needs a new nonce for every encryption. Samsung took a secure cipher mode and implemented it insecurely.

News article.

Security Risks of Relying on a Single Smartphone

Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2021/09/security-risks-of-relying-on-a-single-smartphone.html

Isracard used a single cell phone to communicate with credit card clients, and receive documents via WhatsApp. An employee stole the phone. He reformatted the phone and replaced the SIM card, which was oddly the best possible outcome, given the circumstances. Using the data to steal money would have been much worse.

Here’s a link to an archived version.

Paragon: Yet Another Cyberweapons Arms Manufacturer

Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2021/08/paragon-yet-another-cyberweapons-arms-manufacturer.html

Forbes has the story:

Paragon’s product will also likely get spyware critics and surveillance experts alike rubbernecking: It claims to give police the power to remotely break into encrypted instant messaging communications, whether that’s WhatsApp, Signal, Facebook Messenger or Gmail, the industry sources said. One other spyware industry executive said it also promises to get longer-lasting access to a device, even when it’s rebooted.


Two industry sources said they believed Paragon was trying to set itself apart further by promising to get access to the instant messaging applications on a device, rather than taking complete control of everything on a phone. One of the sources said they understood that Paragon’s spyware exploits the protocols of end-to-end encrypted apps, meaning it would hack into messages via vulnerabilities in the core ways in which the software operates.

Read that last sentence again: Paragon uses unpatched zero-day exploits in the software to hack messaging apps.

New Report on Police Decryption Capabilities

Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2020/10/new-report-on-police-decryption-capabilities.html

There is a new report on police decryption capabilities: specifically, mobile device forensic tools (MDFTs). Short summary: it’s not just the FBI that can do it.

This report documents the widespread adoption of MDFTs by law enforcement in the United States. Based on 110 public records requests to state and local law enforcement agencies across the country, our research documents more than 2,000 agencies that have purchased these tools, in all 50 states and the District of Columbia. We found that state and local law enforcement agencies have performed hundreds of thousands of cellphone extractions since 2015, often without a warrant. To our knowledge, this is the first time that such records have been widely disclosed.

Lots of details in the report. And in this news article:

At least 49 of the 50 largest U.S. police departments have the tools, according to the records, as do the police and sheriffs in small towns and counties across the country, including Buckeye, Ariz.; Shaker Heights, Ohio; and Walla Walla, Wash. And local law enforcement agencies that don’t have such tools can often send a locked phone to a state or federal crime lab that does.


The tools mostly come from Grayshift, an Atlanta company co-founded by a former Apple engineer, and Cellebrite, an Israeli unit of Japan’s Sun Corporation. Their flagship tools cost roughly $9,000 to $18,000, plus $3,500 to $15,000 in annual licensing fees, according to invoices obtained by Upturn.

Interesting Attack on the EMV Smartcard Payment Standard

Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2020/09/interesting-attack-on-the-emv-smartcard-payment-standard.html

It’s complicated, but it’s basically a man-in-the-middle attack that involves two smartphones. The first phone reads the actual smartcard, and then forwards the required information to a second phone. That second phone actually conducts the transaction on the POS terminal. That second phone is able to convince the POS terminal to conduct the transaction without requiring the normally required PIN.

From a news article:

The researchers were able to demonstrate that it is possible to exploit the vulnerability in practice, although it is a fairly complex process. They first developed an Android app and installed it on two NFC-enabled mobile phones. This allowed the two devices to read data from the credit card chip and exchange information with payment terminals. Incidentally, the researchers did not have to bypass any special security features in the Android operating system to install the app.

To obtain unauthorized funds from a third-party credit card, the first mobile phone is used to scan the necessary data from the credit card and transfer it to the second phone. The second phone is then used to simultaneously debit the amount at the checkout, as many cardholders do nowadays. As the app declares that the customer is the authorized user of the credit card, the vendor does not realize that the transaction is fraudulent. The crucial factor is that the app outsmarts the card’s security system. Although the amount is over the limit and requires PIN verification, no code is requested.

The paper: “The EMV Standard: Break, Fix, Verify.”

Abstract: EMV is the international protocol standard for smartcard payment and is used in over 9 billion cards worldwide. Despite the standard’s advertised security, various issues have been previously uncovered, deriving from logical flaws that are hard to spot in EMV’s lengthy and complex specification, running over 2,000 pages.

We formalize a comprehensive symbolic model of EMV in Tamarin, a state-of-the-art protocol verifier. Our model is the first that supports a fine-grained analysis of all relevant security guarantees that EMV is intended to offer. We use our model to automatically identify flaws that lead to two critical attacks: one that defrauds the cardholder and another that defrauds the merchant. First, criminals can use a victim’s Visa contact-less card for high-value purchases, without knowledge of the card’s PIN. We built a proof-of-concept Android application and successfully demonstrated this attack on real-world payment terminals. Second, criminals can trick the terminal into accepting an unauthentic offline transaction, which the issuing bank should later decline, after the criminal has walked away with the goods. This attack is possible for implementations following the standard, although we did not test it on actual terminals for ethical reasons. Finally, we propose and verify improvements to the standard that prevent these attacks, as well as any other attacks that violate the considered security properties.The proposed improvements can be easily implemented in the terminals and do not affect the cards in circulation.