Early Thoughts on Krak

Eric Rand,

The news is coming out today about a core protocol-level flaw in WPA2-PSK named "KRAK" [a forced acronym for Key Renegotiation AttacK, the method by which connections can be compromised]

The concept, based on early reports, appears to be that an attacker can force renegotiation of all or nearly all currently deployed wifi connections in such a fashion that they are subject to eavesdropping or other man-in-the-middle type attacks. This appears to be accomplished via forcing the participants of the connection to use a weak or broken key to secure the connection.

These early reports also suggest that this attack may be limited to WPA connections using pre-shared keys - also known as "WPA Personal" or "WPA-PSK". If WPA with RADIUS is in use [often referred to as "WPA Enterprise"] that may not be subject to this specific kind of attack, as the part of the negotiation thought to be vulnerable takes place after the RADIUS authentication sequence.

The good news is that this attack is limited specifically to the physical wifi layer - meaning that any attacker would need to be in close proximity to your network in order to carry out the attack. This means that exploitation is likely to be relatively slow unless you are being actively targeted at this time - there's only so fast wardrivers can drive.

Also, if you are using a VPN or a TLS-secured connection [that is, securing the connection higher up the protocol stack] then the contents carried by those connections will be unaffected by this attack, other than potentially being slowed down or denied if an attack is actively taking place. 

If you allow access to internal company resources via wifi-mediated connections, then it may be adviseable to disallow such access for the forseeable future until patches or other remediative measures are made available by equipment vendors.

You might also consider turning off wifi entirely and relying on cellular or wired connections for data transport. Cellular connections use a different protocol for negotiating connections, so they are not subject to this attack.

We at Castra will be more than happy to work with you on mitigating this attack, and will update with more information as it becomes available.

Additionally, a solution for integrating wireless IDS information into the Alienvault platform is currently in progress; if you are interested, please contact Castra for details.