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This Monday, a paper published by researchers Mathy Vanhoef and Frank Piessens from KU Leuven in Belgium regarding a security vulnerability in WPA2 (Wi-Fi Protected Access II) caused a seismic shock in the global internet and cybersecurity fields.
The proof-of-concept attack they developed, known as “KRACK” (Key Reinstallation AttaCKs), can allow intruders to easily intercept encrypted data such as credit card information, passwords, chats, emails, and photos.
In some cases, attackers can even inject ransomware or other malicious content into the data packets of the websites users are visiting. The paper states that this vulnerability affects all devices using the WPA2 protocol globally (which includes the vast majority of Wi-Fi devices). In other words, no operating system or device is safe.
On the researchers’ website announcing this vulnerability, they stated that the core mechanism of the WPA2 protocol has a flaw. The principle of KRACK targets the four-way “handshake” that must occur when a user connects to a wireless network using WPA2. This “handshake” is intended to ensure the security of data transmission between the user and the access point by transmitting an encrypted common key as proof.
During the attack, KRACK modifies and replays the encrypted handshake information, enticing the user to install a previously used key. This causes the user to reset the transmitted packet number (Nonce) and the received packet number (Replay Counter) to their initial values, thereby compromising the integrity of the entire encryption system.
In a video recorded by Vanhoef, he demonstrated how to use KRACK to compromise an Android phone. After being lured, the target system successfully reinstalled a key with all values set to zero, allowing the intruder to easily decrypt all data between the phone and the access point. He stated that since such attacks are also effective against Linux, both Linux and Android systems are particularly vulnerable: “Currently, 50% of Android devices can be easily compromised by this particularly severe variant of KRACK.”
Moreover, simply accessing HTTPS (encrypted with SSL, i.e., Secure Sockets Layer) websites and using the HTTPS protocol for multi-layer encryption does not ensure the security of data transmission. Many HTTPS-enabled websites can be forced by third-party software to stop transmitting encrypted HTTPS data and revert to unencrypted HTTP protocol due to improper settings. In the video demonstration, Vanhoef used a script called SSLstrip to force match.com to downgrade from HTTPS to HTTP. As a result, the user’s account and password were easily intercepted and cracked.
The researchers indicated that this vulnerability affects access points, computers, smartphones, and other devices using wireless connections, with the only difference being the difficulty and effectiveness of successfully cracking them. Therefore, all terminal devices using WPA2, such as OpenBSD, MacOS, and Windows, as well as Wi-Fi access points like MediaTek Linksys, can also be compromised by KRACK. Furthermore, in an appendix published by the researchers today, they stated: “Since the paper was submitted for review on May 19, new methods discovered in the past few months mean that MacOS and OpenBSD are even easier to compromise than stated in the original text.” Thus, among common user devices, only Windows and iOS have relatively higher resistance.
The U.S. government’s Computer Emergency Response Team (US-CERT) has issued a warning regarding this vulnerability:
US-CERT recently learned of vulnerabilities in several important management mechanisms within the four-way handshake of the WPA2 protocol. The impacts of exploiting these vulnerabilities include data cracking, packet replay, TCP connection hijacking, HTTP content injection, and more. Note that as a protocol-level issue, the vast majority, if not all, devices using this standard will be affected.
Since the researchers discovered this vulnerability back in May, they had already secretly warned experts in the global cybersecurity community, urging them to immediately begin developing patches. Vanhoef stated that as long as the user has patched their device, it is safe even when connecting to an unpatched access point.
Microsoft issued a statement on Monday explaining the conditions under which hackers could successfully compromise Windows systems, stating that the system update package pushed on October 10 already contains a patch for this vulnerability. (Windows users who have not recently updated their systems should do so immediately). Additionally, Microsoft noted that due to the sleep state, Windows may delegate WPA2 authentication functions to the system’s wireless hardware, so to ensure full security, users should also install the latest drivers for their wireless network cards.
As for other systems, the patch for Linux has been developed, but the specific rollout time for each distribution is still unknown. Since the Android system is developed based on Linux, it is also considered a close relative. Google stated that it will release an Android patch in the “coming weeks,” with its own Pixel phones being the first to receive the patch in the upgrade package on November 6. Apple stated that the vulnerability has been included in the latest beta versions of iOS and MacOS and will be announced in a few weeks.
Major wireless access point (router) companies like Cisco, Netgear, Belkin, and Linksys, as well as major wireless card companies like Intel and Espressif, along with several other companies in the networking field, have also been rolling out patches or announcing that they are working on developing patches in recent days.
However, the most significant impact of this vulnerability is on the vast number of Internet of Things (IoT) wireless smart devices and older networking equipment on the market.
Due to the system updates for IoT devices being influenced by manufacturers, suppliers, and users, the vast majority of IoT devices will receive very few system upgrades after being sold. Since this vulnerability is at the protocol level, i.e., a standard-level vulnerability, developing patches often requires modifications to the device, chip, and operating system.
If these three come from different parties, and any of the three changes, the chances of developing a patch for that device are virtually zero. Even if a vendor provides a patch for a certain device, if the user does not know how to install the patch or is unaware that a patch is needed, the device’s vulnerability may never be addressed throughout its lifetime. Given that most existing IoT devices are security devices like cameras, monitors, and door locks, the risks behind this are not hard to imagine.
As for older networking equipment, such as home routers, their issues are very similar to those of IoT devices. Major manufacturers like Netgear have sold over 1,200 router models. Among these 1,200 models, at least 1,100 are at the end of their product life cycle. This means that even if Netgear patches these products, they are unlikely to have the hardware and software conditions to develop that patch. For the remaining 100 models still in production, although Netgear can develop patches for them, each model requires time, manpower, and resources for development. And this is just for one company’s products. No one knows how many networking devices globally are at the end of their life cycle or lack the resources to develop patches immediately.
Image | Netgear Nighthawk series classic router
From these two points, it is easy to understand why some cybersecurity experts refer to this vulnerability as “the biggest security flaw of the 21st century,” and even “we will still find devices with this vulnerability 20 years from now.”
So, how can we protect ourselves as users? Since almost all common user devices, except for the latest Windows systems, are at risk of being compromised, we should pay close attention to the patches for the systems we use and apply them immediately after they are released.
If your terminal device and wireless access point have not yet been patched, the safest approach is to use a wired network while waiting for the patch. If you have no choice but to use wireless internet, it is best to use secure and reliable protocols such as (properly configured) HTTPS, STARTTLS, Secure Shell, etc., to encrypt your data. If your wireless network device is somewhat outdated, your best option is to purchase a new device to replace it.
Fortunately, the good news is that it was scientists, not hackers, who discovered this vulnerability; otherwise, the consequences could have been unimaginable.
-End-
Reviewed by: Huang Shan
References:
https://www.krackattacks.com/
https://arstechnica.com/information-technology/2017/10/how-the-krack-attack-destroys-nearly-all-wi-fi-security/
https://arstechnica.com/information-technology/2017/10/severe-flaw-in-wpa2-protocol-leaves-wi-fi-traffic-open-to-eavesdropping/
https://www.theverge.com/2017/10/16/16481136/wpa2-wi-fi-krack-vulnerability
https://www.theverge.com/2017/10/16/16481252/wi-fi-hack-attack-android-wpa-2-details
https://www.theverge.com/2017/10/16/16481818/wi-fi-attack-response-security-patches
https://www.dailydot.com/debug/public-wifi-krack-wpa2-flaw/
