KRACK Attack: How Enterprises Can Protect Their WiFi

By this time you've probably heard about the KRACK attack, and what you've heard is right. This one is bad, and it's everywhere.

The name is an acronym taken from key reinstallation attacks, the technique used to take advantage of a vulnerability that exists in pretty much every WiFi access point in use today. The reason it's so widespread is that the vulnerability in the way WPA2 (WiFi Protected Access II) is implemented in the WiFi protocol.

Here, in a nutshell is the problem: In WPA2 there's a shared secret (the password) that a device and the access point use to begin the process, and then a single-use string (or "nonce") that is shared to actually encrypt the conversation. This happens in a process known as a four-way handshake. The vulnerability is in step three of the four-way handshake, when an attacker can force the access point to re-use a previous nonce -- a nonce that the attacker has.

Once the bogus nonce is in use, the attacker can decrypt the entire session and steal any information passing over the network. Now, if this is happening on a public network where employees have already been trained to use a VPN, then there's no real problem since sensitive traffic will travel within an ecnrypted tunnel and the encryption used by SSL and most other VPNs isn't affected by the vulnerability.

The issue is with corporate WiFi networks (and home networks where the employee has implemented WPA2) in which people have been trained to think of traffic as secure, and VPNs as unnecessary. There are few situations more dangerous than one in which people think they're far more secure than they actually are -- and this KRACK attack combines that with near ubiquity.

If there's good news to be found in all this, it's that there haven't been any attacks based on this technique identified in the wild. The news gets a little better with both Microsoft and Apple announcing that they have patches either released or in beta for their desktop and mobile operating systems (though there hasn't been any news, yet, about Apple patching the software for their Airport WiFi access points).

US-CERT has a vulnerability note on the WPA2 vulnerability and they've thoughtfully included a list of vendors affected by the problem.

So what is an enterprise to do? First, at least temporarily amend your WiFi use rules to include VPN use at all times -- even when connected to wireless networks inside the perimeter. Next, stay on top of your vendors for patches to device and access point software. Some have suggested that companies use this episode as a pass/fail test for vendors: If they don't patch vulnerable systems, and soon, then replace them with vendors that pay more attention to security.

How is your organization reponsing to KRACK? We would like to hear your stories -- let us know in the comment section, below.

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— Curtis Franklin is the editor of SecurityNow.com. Follow him on Twitter @kg4gwa.