Risk: Medium
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.
The weakness allows mischievous users to take down networks within five seconds. Any organisation that relies heavily on wireless infrastructure should take the threat seriously and evaluate those networks. If at all possible, a move back to wired systems for critical systems is highly recommended.
While previous denial of service attacks against wireless networks have required specialist 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.
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.
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, 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 are to be presented to the Institute of Electrical and Electronic Engineers (IEEE) Wireless Telecommunication Symposium in California.