Menu
Get Support
Free Discovery Session

Attackers Can Intercept Passwords and More Due to Serious Flaw in WPA2 Protocol

Peerless Tech Solutions
October 17, 2017

A flaw was discovered by researchers in the WPA2 protocol that allows attackers within range of vulnerable device or access point to intercept e-mails, passwords, and other data presumed to be encrypted, and insert ransomware or other malicious content into a website someone is visiting.

The exploit is called KRACK, known for Key Reinstallation Attacks. The research has been kept a secret for weeks ahead of the scheduled time for release at 8 am Monday, EST. A website discussing the vulnerability said it affects the core WPA2 protocol and is effective against devices running Android, Linux, and OpenBSD, and not as extreme macOS and Windows, as well as MediaTek Linksys, and other types of devices. The site warned that attackers can exploit the flaw to decrypt a wealth of sensitive data that's normally encrypted by the nearly ubiquitous Wi-Fi encryption protocol.

"This can be abused to steal sensitive information such as credit card numbers, passwords, chat messages, emails, photos, and so on," researcher Mathy Vanhoef, of the Katholieke Universiteit Leuven in Belgium wrote. "The attack works against all modern protected Wi-Fi networks. Depending on the network configuration, it is also possible to inject and manipulate data. For example, an attacker might be able to inject ransomware or other malware into websites."

Vanhoef released this video displaying the attack against a device running Google's Android mobile operating system:

[embed]https://www.youtube.com/watch?time_continue=1&v=Oh4WURZoR98[/embed]

The video shows the attacker decrypting all the data a phone sends to an access point. The attack works by forcing the phone into reinstalling an all-zero encryption key, rather than the real key. This ability, which also works on Linux, makes the attack particularly effective on these platforms. The attack is through a wireless connection that can happen anywhere at any time.

Visiting only HTTPS-protected Web pages isn't automatically a remedy against the attack, since many improperly configured sites can be forced into dropping encrypted HTTPS traffic and instead transmitting unencrypted HTTP data. In the video, the attacker uses a script known as SSLstrip to force the site match.com to downgrade a connection to HTTP. The attacker then can steal an account password when the Android device logs in.

"Although websites or apps may use HTTPS as an additional layer of protection, we warn that this extra protection can (still) be bypassed in a worrying number of situations," the researchers explained. "For example, HTTPS was previously bypassed in non-browser software, in Apple's iOS and OS X, in Android apps, in Android apps again, in banking apps, and even in VPN apps."

The weakness allows attackers to target both vulnerable access points, computers, smartphones and other types of connecting clients, albeit with differing levels of difficulty and effectiveness. Neither Windows nor iOS are believed to be vulnerable to the most severe attacks. Linux and Android appear to be more susceptible, because attackers can force network decryption on clients in seconds with little effort.

Vanhoef said clients can be patched to prevent attacks even when connected to vulnerable access points. Linux patches have been developed, but it's not immediately clear when they will become available for various distributions and for Android users. Patches are also available for some but not all Wi-fi access points.

KRACK works by targeting a four-way handshake that's executed when a client joins a WPA2-protected Wi-Fi network. Among other things, the handshake helps to confirm that both the client and access points have the correct credentials. KRACK tricks the vulnerable client into reinstalling an already-in-use key. The reinstallation forces the client to reset packet numbers containing a cryptographic nonce and other parameters to their initial values. KRACK forces the nonce reuse in a way that allows the encryption to be bypassed.

According to a researcher who has been briefed on the vulnerability, it works by exploiting a four-way handshake that's used to establish a key for encrypting traffic. During the third step, the key can be resent multiple times. When it's resent in certain ways, a cryptographic nonce can be reused in a way that completely undermines the encryption.

KRACK came to light on Sunday when people discovered a Github page belonging to one of the researchers and a separate krackattacks.com website disclosing the vulnerability used the following tags:

  • WPA2
  • KRACK
  • key reinstallation
  • security protocols
  • network security, attacks
  • nonce reuse
  • handshake
  • packet number
  • initialization vector
Researchers briefed on the vulnerabilities said they are indexed as: CVE-2017-13077, CVE-2017-13078, CVE-2017-13079, CVE-2017-13080, CVE-2017-13081, CVE-2017-13082, CVE-2017-13084, CVE-2017-13086, CVE-2017-13087, CVE-2017-13088. One researcher told Ars that Aruba and Ubiquiti, which sell wireless access points to large corporations and government organizations, already have updates available to patch or mitigate the vulnerabilities.

 

The vulnerability is likely to pose the biggest threat to large corporate and government Wi-Fi networks, particularly if they accept connections from Linux and Android devices. And once again, attackers must be within Wi-Fi range of a vulnerable access point or client to pull off the attacks. Home Wi-Fi  users are vulnerable, too, again especially if they connect with Linux or Android devices, but there are likely easier ways they can be attacked.

Microsoft on Monday posted an advisory here that explains the conditions that are necessary for attackers to exploit vulnerable Windows machines. The company issued an update during last week's Patch Tuesday release that fixes the problem. Windows users who have yet to install the patch should do so right away. Microsoft's advisory said even when patched, affected Windows system may offload vulnerable WPA2 functionality to installed Wi-Fi hardware when devices enter low-power standby modes. To fully protect themselves, users should also install new Wi-Fi device drivers if available, in addition to the Windows fix.

If possible, people with vulnerable access points and clients should avoid using Wi-Fi until patches are available and instead use wired connections. When Wi-Fi is the only connection option, people should use HTTPS, STARTTLS, Secure Shell, and other reliable protocols to encrypt Web and e-mail traffic as it passes between computers and access points. As a fall-back users should consider using a virtual private network as an added safety measure, but users are reminded to choose their VPN providers carefully, since many services can't be trusted to make users more secure.

Want to learn more about how to keep your devices safe from malicious Wi-Fi? Call us today.

Don't Miss an Article!

Subscribe by Email

Get The Latest From Peerless Right in Your Inbox