Entries Tagged "Wi-Fi"

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Counting People through a Wall with Wi-Fi

Interesting research:

In the team’s experiments, one WiFi transmitter and one WiFi receiver are behind walls, outside a room in which a number of people are present. The room can get very crowded with as many as 20 people zigzagging each other. The transmitter sends a wireless signal whose received signal strength (RSSI) is measured by the receiver. Using only such received signal power measurements, the receiver estimates how many people are inside the room ­ an estimate that closely matches the actual number. It is noteworthy that the researchers do not do any prior measurements or calibration in the area of interest; their approach has only a very short calibration phase that need not be done in the same area.

Academic paper.

Posted on September 27, 2018 at 7:43 AMView 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 PMView Comments

WPA3

Everyone is writing about the new WPA3 Wi-Fi security standard, and how it improves security over the current WPA2 standard.

This summary is as good as any other:

The first big new feature in WPA3 is protection against offline, password-guessing attacks. This is where an attacker captures data from your Wi-Fi stream, brings it back to a private computer, and guesses passwords over and over again until they find a match. With WPA3, attackers are only supposed to be able to make a single guess against that offline data before it becomes useless; they’ll instead have to interact with the live Wi-Fi device every time they want to make a guess. (And that’s harder since they need to be physically present, and devices can be set up to protect against repeat guesses.)

WPA3’s other major addition, as highlighted by the Alliance, is forward secrecy. This is a privacy feature that prevents older data from being compromised by a later attack. So if an attacker captures an encrypted Wi-Fi transmission, then cracks the password, they still won’t be able to read the older data — they’d only be able to see new information currently flowing over the network.

Note that we’re just getting the new standard this week. Actual devices that implement the standard are still months away.

Posted on July 12, 2018 at 6:11 AMView Comments

Needless Panic Over a Wi-FI Network Name

A Turkish Airlines flight made an emergency landing because someone named his wireless network (presumably from his smartphone) “bomb on board.”

In 2006, I wrote an essay titled “Refuse to be Terrorized.” (I am also reminded of my 2007 essay, “The War on the Unexpected.” A decade later, it seems that the frequency of incidents like the one above is less, although not zero. Progress, I suppose.

Posted on December 1, 2017 at 9:56 AMView Comments

New KRACK Attack Against Wi-Fi Encryption

Mathy Vanhoef has just published a devastating attack against WPA2, the 14-year-old encryption protocol used by pretty much all Wi-Fi systems. It’s an interesting attack, where the attacker forces the protocol to reuse a key. The authors call this attack KRACK, for Key Reinstallation Attacks.

This is yet another of a series of marketed attacks; with a cool name, a website, and a logo. The Q&A on the website answers a lot of questions about the attack and its implications. And lots of good information in this ArsTechnica article.

There is an academic paper, too:

“Key Reinstallation Attacks: Forcing Nonce Reuse in WPA2,” by Mathy Vanhoef and Frank Piessens.

Abstract: We introduce the key reinstallation attack. This attack abuses design or implementation flaws in cryptographic protocols to reinstall an already-in-use key. This resets the key’s associated parameters such as transmit nonces and receive replay counters. Several types of cryptographic Wi-Fi handshakes are affected by the attack. All protected Wi-Fi networks use the 4-way handshake to generate a fresh session key. So far, this 14-year-old handshake has remained free from attacks, and is even proven secure. However, we show that the 4-way handshake is vulnerable to a key reinstallation attack. Here, the adversary tricks a victim into reinstalling an already-in-use key. This is achieved by manipulating and replaying handshake messages. When reinstalling the key, associated parameters such as the incremental transmit packet number (nonce) and receive packet number (replay counter) are reset to their initial value. Our key reinstallation attack also breaks the PeerKey, group key, and Fast BSS Transition (FT) handshake. The impact depends on the handshake being attacked, and the data-confidentiality protocol in use. Simplified, against AES-CCMP an adversary can replay and decrypt (but not forge) packets. This makes it possible to hijack TCP streams and inject malicious data into them. Against WPA-TKIP and GCMP the impact is catastrophic: packets can be replayed, decrypted, and forged. Because GCMP uses the same authentication key in both communication directions, it is especially affected.

Finally, we confirmed our findings in practice, and found that every Wi-Fi device is vulnerable to some variant of our attacks. Notably, our attack is exceptionally devastating against Android 6.0: it forces the client into using a predictable all-zero encryption key.

I’m just reading about this now, and will post more information as I learn it.

EDITED TO ADD: More news.

EDITED TO ADD: This meets my definition of brilliant. The attack is blindingly obvious once it’s pointed out, but for over a decade no one noticed it.

EDITED TO ADD: Matthew Green has a blog post on what went wrong. The vulnerability is in the interaction between two protocols. At a meta level, he blames the opaque IEEE standards process:

One of the problems with IEEE is that the standards are highly complex and get made via a closed-door process of private meetings. More importantly, even after the fact, they’re hard for ordinary security researchers to access. Go ahead and google for the IETF TLS or IPSec specifications — you’ll find detailed protocol documentation at the top of your Google results. Now go try to Google for the 802.11i standards. I wish you luck.

The IEEE has been making a few small steps to ease this problem, but they’re hyper-timid incrementalist bullshit. There’s an IEEE program called GET that allows researchers to access certain standards (including 802.11) for free, but only after they’ve been public for six months — coincidentally, about the same time it takes for vendors to bake them irrevocably into their hardware and software.

This whole process is dumb and — in this specific case — probably just cost industry tens of millions of dollars. It should stop.

Nicholas Weaver explains why most people shouldn’t worry about this:

So unless your Wi-Fi password looks something like a cat’s hairball (e.g. “:SNEIufeli7rc” — which is not guessable with a few million tries by a computer), a local attacker had the capability to determine the password, decrypt all the traffic, and join the network before KRACK.

KRACK is, however, relevant for enterprise Wi-Fi networks: networks where you needed to accept a cryptographic certificate to join initially and have to provide both a username and password. KRACK represents a new vulnerability for these networks. Depending on some esoteric details, the attacker can decrypt encrypted traffic and, in some cases, inject traffic onto the network.

But in none of these cases can the attacker join the network completely. And the most significant of these attacks affects Linux devices and Android phones, they don’t affect Macs, iPhones, or Windows systems. Even when feasible, these attacks require physical proximity: An attacker on the other side of the planet can’t exploit KRACK, only an attacker in the parking lot can.

EDITED TO ADD (11/13): The official link to the paper blocks anonymous users. Here’s an alternate.

Posted on October 16, 2017 at 8:39 AMView Comments

Amazon Patents Measures to Prevent In-Store Comparison Shopping

Amazon has been issued a patent on security measures that prevents people from comparison shopping while in the store. It’s not a particularly sophisticated patent — it basically detects when you’re using the in-store Wi-Fi to visit a competitor’s site and then blocks access — but it is an indication of how retail has changed in recent years.

What’s interesting is that Amazon is on the other side of this arms race. As an on-line retailer, it wants people to walk into stores and then comparison shop on its site. Yes, I know it’s buying Whole Foods, but it’s still predominantly an online retailer. Maybe it patented this to prevent stores from implementing the technology.

It’s probably not nearly that strategic. It’s hard to build a business strategy around a security measure that can be defeated with cellular access.

Posted on June 23, 2017 at 6:26 AMView Comments

Using Wi-Fi to Get 3D Images of Surrounding Location

Interesting research:

The radio signals emitted by a commercial Wi-Fi router can act as a kind of radar, providing images of the transmitter’s environment, according to new experiments. Two researchers in Germany borrowed techniques from the field of holography to demonstrate Wi-Fi imaging. They found that the technique could potentially allow users to peer through walls and could provide images 10 times per second.

News article.

Posted on May 16, 2017 at 6:08 AMView Comments

Many Android Phones Vulnerable to Attacks Over Malicious Wi-Fi Networks

There’s a blog post from Google’s Project Zero detailing an attack against Android phones over Wi-Fi. From Ars Technica:

The vulnerability resides in a widely used Wi-Fi chipset manufactured by Broadcom and used in both iOS and Android devices. Apple patched the vulnerability with Monday’s release of iOS 10.3.1. “An attacker within range may be able to execute arbitrary code on the Wi-Fi chip,” Apple’s accompanying advisory warned. In a highly detailed blog post published Tuesday, the Google Project Zero researcher who discovered the flaw said it allowed the execution of malicious code on a fully updated 6P “by Wi-Fi proximity alone, requiring no user interaction.”

Google is in the process of releasing an update in its April security bulletin. The fix is available only to a select number of device models, and even then it can take two weeks or more to be available as an over-the-air update to those who are eligible. Company representatives didn’t respond to an e-mail seeking comment for this post.

The proof-of-concept exploit developed by Project Zero researcher Gal Beniamini uses Wi-Fi frames that contain irregular values. The values, in turn, cause the firmware running on Broadcom’s wireless system-on-chip to overflow its stack. By using the frames to target timers responsible for carrying out regularly occurring events such as performing scans for adjacent networks, Beniamini managed to overwrite specific regions of device memory with arbitrary shellcode. Beniamini’s code does nothing more than write a benign value to a specific memory address. Attackers could obviously exploit the same series of flaws to surreptitiously execute malicious code on vulnerable devices within range of a rogue access point.

Slashdot thread.

Posted on April 6, 2017 at 7:52 AMView Comments

Using Wi-Fi to Detect Hand Motions and Steal Passwords

This is impressive research: “When CSI Meets Public WiFi: Inferring Your Mobile Phone Password via WiFi Signals“:

Abstract: In this study, we present WindTalker, a novel and practical keystroke inference framework that allows an attacker to infer the sensitive keystrokes on a mobile device through WiFi-based side-channel information. WindTalker is motivated from the observation that keystrokes on mobile devices will lead to different hand coverage and the finger motions, which will introduce a unique interference to the multi-path signals and can be reflected by the channel state information (CSI). The adversary can exploit the strong correlation between the CSI fluctuation and the keystrokes to infer the user’s number input. WindTalker presents a novel approach to collect the target’s CSI data by deploying a public WiFi hotspot. Compared with the previous keystroke inference approach, WindTalker neither deploys external devices close to the target device nor compromises the target device. Instead, it utilizes the public WiFi to collect user’s CSI data, which is easy-to-deploy and difficult-to-detect. In addition, it jointly analyzes the traffic and the CSI to launch the keystroke inference only for the sensitive period where password entering occurs. WindTalker can be launched without the requirement of visually seeing the smart phone user’s input process, backside motion, or installing any malware on the tablet. We implemented Windtalker on several mobile phones and performed a detailed case study to evaluate the practicality of the password inference towards Alipay, the largest mobile payment platform in the world. The evaluation results show that the attacker can recover the key with a high successful rate.

That “high successful rate” is 81.7%.

News article.

Posted on November 18, 2016 at 6:40 AMView Comments

Sidebar photo of Bruce Schneier by Joe MacInnis.