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What are FragAttacks? How to secure your WiFi against FragAttacks?



Just about recently, a security researcher has discovered and reported new vulnerabilities in WiFi devices known as FragAttacks. These are new types of attacks that exploit design flaws in the WiFi standard and affect most WiFi-enabled devices. He has previously discovered the KRACK attack which basically affected WPA2 protocol.


What are FragAttacks?

FragAttacks term is coined with the phrase Fragmentation and Aggregation Attacks. These are security threats that target WiFi devices. In these attacks, the attacker basically targets a device that is within the range of its WiFi network and steals the victim’s sensitive information (e.g., password). These attacks impact all recent WiFi security protocols including WPA3 and WPA2. Home routers, IoT, smartphones, and many other devices are affected by these kinds of attacks.



Design Flaws in WiFi

FragAttacks take advantage of several vulnerabilities in WiFi. They can be carried out in various ways including:

The attacker may inject an unencrypted WiFi frame into a secure WiFi network. They can use the first design flaw in the WiFi standard which is its aggregation feature. In this, the “is aggregated” flag in a frame is not validated and can easily be modified. Hence, the attacker injects the packet and tricks the victim into redirecting him to their malicious server.


The second design flaw in WiFi is its frame fragmentation feature and is known as a mixed key attack. The fragments from the same frame are encrypted with the same key, while the receiver can reassemble fragments with different keys. An attacker can use this to exfiltrate the victim’s data.


The third design flaw is again with the frame fragmentation feature in WiFi and is called fragment cache attack. What happens is that the WiFi device doesn’t eliminate non-reassembled fragments from memory when a user is disconnected from a network. This can be exploited by injecting a malicious fragment into the access point’s memory. Now, when a user connects to the WiFi network and transmits a fragmented frame, those fragments will be reassembled with the attacker’s injected malicious fragment.


How to secure your WiFi against FragAttacks?

Some standard practices can help you protect your WiFi from FragAttacks. These are:

  1. Upgrade your device

  2. Install Security Updates

  3. Use Encryption

  4. Use a VPN

  5. Set up a Custom DNS


1] Upgrade your device

Mathy Vanhoef says in his blog:

The biggest risk in practice is likely the ability to abuse the discovered flaws to attack devices in someone’s home network. For instance, many smart home and internet-of-things devices are rarely updated, and Wi-Fi security is the last line of defense that prevents someone from attacking these devices. Unfortunately, due to the discover vulnerabilities, this last line of defense can now be bypassed. In the demo above, this is illustrated by remotely controlling a smart power plug and by taking over an outdated Windows 7 machine.

So, if you are using an older version of your devices, you must upgrade them. For example, if you are still using Windows 7/8, it’s the right time to upgrade to Windows 10 to protect your device against FragAttacks and other new security attacks.


And, if you are using an old router that has no upgrades available for a long, you must consider changing your router and getting a new one. Simply replace your device if there are no firmware updates regularly.


2] Install Security Updates

Always make sure that you have installed security updates on your device. Security updates help you protect your devices against any new vulnerability and security attacks. So, keep on checking for security updates and install them as soon as they are available. Although, smartphones and other modern devices automatically download and install security updates. But, also check manually to ensure the same.


In the case of Windows 10, you can install security and other updates by going to the Settings > Update & Security > Windows Update option and check for updates available and then download and install them on your PC.


3] Use Encryption

When browsing online, ensure that you are on a secure website with an HTTPS (Hypertext Transfer Protocol Secure) certificate. Not just that, use encryption all the time and everywhere. For example, use a secure application that offers end-to-end encryption to transfer data between devices. Remember FragAttacks occur when unencrypted data is sent over a secure network. So, encryption is a must.


4] Use a VPN

Consider using a VPN service as it can provide you protection against FragAttacks by routing your traffic through an encrypted connection.


5] Set up a Custom DNS

You can also configure a custom DNS manually in your router and other devices to obstruct any attack that redirects you to a malicious server.


FragAttacks are a new collection of vulnerabilities in WiFi standard that puts multiple devices at risk. An attacker within the range of your network can carry out these types of attacks where he attempts to steal your data. However, some basic security practices can help you protect your WiFi against FragAttacks.



Source: Windowsclub


The Tech Platform

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