All Wi-Fi networks secured and protected with the Wi-Fi Protected Access 2 (WPA2) are vulnerable to a newly-discovered vulnerability that will potentially affect virtually every device that connects to the internet using Wi-Fi.
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Introduced in 2004, WPA2 is the successor security standard to the second-generation WPA standard, which itself replaced the original Wired Equivalent Privacy (WEP) standard. It is considered stronger and more reliable than its predecessor, and is essentially in universal use around the world.
The vulnerability was uncovered by Mathy Vanhoef, a security expert at KU Leuven University in Belgium, who said attackers could exploit weakness in the standard itself – not in any products or implementations – to read encrypted data, and inject ransomware or malware into websites using a novel technique called a key reinstallation attack (Krack).
A so-called Krack attack targets the four-way handshake in the WPA2 protocol that is executed whenever a client tries to join a protected Wi-Fi network. It confirms that both client and access point (AP) have the right password credentials, and negotiates a new key to encrypt subsequent session traffic.
Vanhoef said that by manipulating and replaying these cryptographic handshake messages, a hacker could trick a device into reinstalling an already-in-use key, giving the attacker visibility of any transmitted data.
The fact that the flaw is in the standard makes it particularly dangerous because any correct implementation of WPA2 anywhere in the world is likely to be affected, said Vanhoef, who will present his research at the Computer and Communications Security Conference and at Black Hat Europe.
In a proof-of-concept demo, Vanhoef carried out a Krack attack on an Android smartphone, and was able to decrypt all data transmitted after tricking the device into reinstalling an in-use key. Android and Linux devices are particularly vulnerable, he added, because their encryption keys can be rewritten to all zeros.
“To prevent the attack, users must update affected products as soon as security updates become available,” wrote Vanhoef. “Note that if your device supports Wi-Fi, it is most likely affected. During our initial research, we discovered ourselves that Android, Linux, Apple, Windows, OpenBSD, MediaTek, Linksys and others are all affected by some variant of the attacks.”
In a statement, the US’s Computer Emergency Readiness Team (US-CERT) said it was aware of the vulnerability, and issued its own warning: “The impact of exploiting these vulnerabilities includes decryption, packet replay, TCP connection hijacking, HTTP content injection, and others. Note that as protocol-level issues, most or all correct implementations of the standard will be affected.”
A spokesperson for the UK’s National Cyber Security Centre (NCSC) moved to downplay the initial impact of the vulnerability. “Research has been published today (16 October) into potential global weaknesses to Wi-Fi systems,” the spokesperson said. “The attacker would have to be physically close to the target and the potential weaknesses would not compromise connections to secure websites, such as banking services or online shopping.
“We are examining the research and will be providing guidance if required. Internet security is a key NCSC priority and we continuously update our advice on issues such as Wi-Fi safety, device management and browser security.”
Lee Munson, security researcher at Comparitech, said the fact that an attacker would need to be within wireless range of a device seemed to indicate than any Krack attacks in the wild will be targeted, rather than random, but he added that it was still very important for users – particularly home users – to be on the alert.
“Until the issue is fixed via a router firmware update – if possible – or WPA2 is superseded, everyone should adopt an additional level of caution when sending sensitive information to online servers,” he said.
“Users are advised to look out for the padlock symbol in their browser, or the addition of the letter ‘s’ on the end of the http part of a web address, before sharing personal or financial information – advice that is more valuable now than ever before.”
It is understood that major technology companies and Wi-Fi hardware suppliers have been aware of the vulnerability since the end of August. ………………………………………………………………………………………………………