[IP] New flaw takes Wi-Fi off the air

[Dave Farber <dave@xxxxxxxxxx>]

Delivered-To: dfarber+@xxxxxxxxxxxxxxxxxx
Date: Thu, 13 May 2004 15:23:54 -0700
From: Dewayne Hendricks <dewayne@xxxxxxxxxxxxx>
Subject: [Dewayne-Net] New flaw takes Wi-Fi off the air
Sender: dewayne-net@xxxxxxxxxxxxx
To: Dewayne-Net Technology List <dewayne-net@xxxxxxxxxxxxx>

New flaw takes Wi-Fi off the air
By Patrick Gray, Security Focus (drew.cullen@xxxxxxxxxxxxxxxxx)
Published Thursday 13th May 2004 21:29 GMT
<http://www.theregister.co.uk/2004/05/13/wifi_security_flaw/>

A newly-discovered vulnerability in the 802.11 wireless standard allows 
attackers to jam wireless networks within a radius of one kilometre using 
off-the-shelf equipment.

Affecting various hardware implementations of the IEEE 802.11 wireless 
networking standard - including widely used 802.11b devices - the flaw was 
found in the collision avoidance routines used to prevent multiple devices 
from transmitting at the same moment.

"When under attack, the device behaves as if the channel is always busy, 
preventing the transmission of any data over the wireless network," a 
security advisory (http://www.auscert.org.au/render.html?it=4091) released 
by AusCERT reads.

The weakness allows miscreants to take down networks within five seconds, 
according to researchers at Australia's Queensland University of 
Technology's Information Security Research Centre (ISRC), which discovered 
the vulnerability.

ISRC's leader of network and systems security research, Associate Professor 
Mark Looi, whose PhD students, Christian Wullems, Kevin Tham and Jason 
Smith discovered the flaw, said any organization that relies heavily on 
wireless infrastructure should take the threat seriously.

"Anyone who's relying on the availability of a wireless network should 
really consider that their wireless network can be knocked offline at any 
time," said Looi. "They need to very seriously evaluate that network and 
decide if it's possible to move away from wireless technology."

While previous denial of service attacks against wireless networks have 
required specialised hardware and relied on high-power antennas, the new 
attack will make knocking a wireless network off the air an option for a 
"semi-skilled" attacker using standard hardware.

"An attacker using a low-powered, portable device such as an electronic PDA 
and a commonly available wireless networking card may cause significant 
disruption to all WLAN traffic within range, in a manner that makes 
identification... of the attacker difficult," The AusCERT advisory read.

Because the flaw is in the 802.11 protocol itself, the vulnerability cannot 
be mitigated through the use of software or encryption schemes. Replacing 
wireless devices with those not affected by the flaw seems the only option, 
said Looi.

"Mitigation strategies are few and far between," Looi said "Organisations 
could deploy wireless networks that don't use this technology, [but] it 
will be a very expensive exercise."

The flaw is only present in devices using a Direct Sequence Spread Spectrum 
(DSSS) physical layer, including IEEE 802.11, 802.11b and 802.11g wireless 
devices operating at low speed. 802.11a and 802.11g wireless devices 
configured to operate at speeds above 20Mbps are not affected by the glitch,

AusCERT senior security analyst Jamie Gillespie does not anticipate the 
wide exploitation of the vulnerability.

"For the average corporate user, we're not expecting to see ongoing denial 
of service attacks. However, if you have remote equipment that is only 
connected through wireless it is possible that the connection could be 
disrupted," Gillespie said. "Some critical infrastructure providers may not 
deploy wireless... but if any do then they should be looking at mitigation 
strategies."

The lack of a "measurable result" during an attack is likely to render the 
average attacker bored, Gillespie added.

Unlike flaws discovered in the WEP encryption scheme, the newly-disclosed 
vulnerability will not allow an attacker to snoop on network communications.

The ISRC findings will be presented to the Institute of Electrical and 
Electronic Engineers (IEEE) Wireless Telecommunication Symposium in 
California on Friday.

Archives at: <http://Wireless.Com/Dewayne-Net>
Weblog at: <http://weblog.warpspeed.com>

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