As anyone reading these pages with regularity knows, I am definitely not for the widespread usage of Wi-Fi for the solution to internet connectivity to the masses. Not only is it slow, prone to interference, and limited by the vagaries of radio transmission and reception, it is less secure than a wired connection (in most cases).

A story from PC World shows that the highly regarded, and currently best, encryption method in use for Wi-Fi, WPA2, has recently been found to have a problem that, according to the finder, has no solution under current standards.

The “Hole 196” problem is described in very few words by the man who discovered the flaw, and he will be demonstrating the problem next week at two conferences in Las Vegas where these attacks are always shown as proof to the hacking community.

Perhaps it was only a matter of time. But wireless security researchers say they have uncovered a vulnerability in the WPA2 security protocol, which is the strongest form of Wi-Fi encryption and authentication currently standardized and available.

Malicious insiders can exploit the vulnerability, named “Hole 196” by the researcher who discovered it at wireless security company AirTight Networks. The moniker refers to the page of the IEEE 802.11 Standard (Revision, 2007) on which the vulnerability is buried.

Hole 196 lends itself to man-in-the-middle-style exploits, whereby an internal, authorized Wi-Fi user can decrypt, over the air, the private data of others, inject malicious traffic into the network and compromise other authorized devices using open source software, according to AirTight.

The researcher who discovered Hole 196, Md Sohail Ahmad, AirTight technology manager, intends to demonstrate it at two conferences taking place in Las Vegas next week: Black Hat Arsenal and DEF CON 18.

The Advanced Encryption Standard (AES) derivative on which WPA2 is based has not been cracked and no brute force is required to exploit the vulnerability, Ahmad says. Rather, a stipulation in the standard that allows all clients to receive broadcast traffic from an access point (AP) using a common shared key creates the vulnerability when an authorized user uses the common key in reverse and sends spoofed packets encrypted using the shared group key.

Ahmad explains it this way:

WPA2 uses two types of keys: 1) Pairwise Transient Key (PTK), which is unique to each client, for protecting unicast traffic; and 2) Group Temporal Key (GTK) to protect broadcast data sent to multiple clients in a network. PTKs can detect address spoofing and data forgery. “GTKs do not have this property,” according to page 196 of the IEEE 802.11 standard.

These six words comprise the loophole, Ahmad says.

Because a client has the GTK protocol for receiving broadcast traffic, the user of that client device could exploit GTK to create its own broadcast packet. From there, clients will respond to the sending MAC address with their own private key information.

Ahmad says it took about 10 lines of code in open source MadWiFi driver software, freely available on the Internet, and an off-the-shelf client card for him to spoof the MAC address of the AP, pretending to be the gateway for sending out traffic. Clients who receive the message see the client as the gateway and “respond with PTKs”, which are private and which the insider can decrypt, Ahmad explains.

From there, “the malicious insider could drop traffic, drop a [denial-of-service] attack, or snoop,” Ahmad says.

The ability to exploit the vulnerability is limited to authorized users, AirTight says. Still, year-after-year security studies show that insider security breaches continue to be the biggest source of loss to businesses, whether from disgruntled employees or spies who steal and sell confidential data.

What can we do about Hole 196?

“There’s nothing in the standard to upgrade to in order to patch or fix the hole,” says Kaustubh Phanse, AirTight’s wireless architect who describes Hole 196 as a “zero-day vulnerability that creates a window of opportunity” for exploitation.

As we can see, it will not be something that little Johnny, the 9-year-old “network genius” will be doing next week, but you can be that there will be some industrial espionage based upon this attack soon, and no doubt some unlucky home users will eventually feel its sting – just because that is the way these things go.

The odds will be low, but for anyone really concerned with safety, perhaps that purchase of the Cat 6 cable to route the small business network, or the home network of the person who works at home might be a really good idea.

Also, remembering that these things develop over time might be a good idea for those who use mobile devices that can make use of Wi-Fi networks.

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Never go to a doctor whose office plants have died.

Erma Bombeck

You could be like this guy, if you have nothing to lose over a Wi-Fi connection…

alfred_e_neuman - what, me worry?


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