'Indefensible' Wi-Fi flaw discovered in 802.11b network protocol

Computerworld - Two security organizations have issued alerts warning of a flaw in wireless LAN equipment based on the 802.11b Wi-Fi standard that leaves the devices vulnerable to a denial-of-service (DoS) jamming attack.
The Australian Computer Emergency Response Team (AusCERT) issued a security alert last Thursday, as did the U.S. Computer Emergency Readiness Team (US-CERT), which warned of the potential threat to wireless networks.
The two organizations, as well as WLAN manufacturers, were notified in November of the flaw, according to Mark Looi, an associate professor at the School of Software Engineering and Data Communications at Queensland University. Three of his Ph.D. students at the Brisbane, Australia-based school -- Christian Wullems, Kevin Tham and Jason Smith -- discovered the flaw.
Since then, Looi said, he and AusCERT have worked with the WLAN manufacturers to find a "mitigation strategy" for the vulnerability before releasing the results of their research. The manufacturers finally concluded that "there are no mitigation strategies available" to rectify the fundamental problem in the 802.11b direct-sequence spread spectrum (DSSS) modulation scheme, Looi said. 802.11b WLANs have a raw data rate of 11Mbit/sec. and operate in the 2.4-GHz frequency band.
The manufacturers indicated that the only solution would be for users to switch to devices using the 802.11a protocol, which uses a different form of modulation than 802.11b, according to Looi.
Last week's security bulletins note that high-speed versions of wireless equipment based on the 802.11g protocol would also be immune to the vulnerability. But only equipment that carries data at speeds above 20Mbit/sec. could be considered safe from the DoS attacks.

"Independent vendors have confirmed that there is currently no defense against this type of attack for DSSS-based WLANs," AusCERT said. "At this time, a comprehensive solution in the form of software or firmware upgrade is not available for retrofit to existing devices. Fundamentally, the issue is inherent in the protocol implementation of IEEE 802.11 DSSS."
James Gillespie, a senior security analyst at AusCERT, said WLAN vendors were given enough time to conduct an investigation of the vulnerability, but he declined to say exactly when industry leaders were notified. AusCERT sent out notification of the flaw through a network operated by the Forum of Incident Response and CERT Teams, which in turn notified country and vendor CERT organizations.
Major WLAN vendors reached today said they are checking on when they first learned of the flaw.
Frank Hanzlik, managing director of the Wi-FI Alliance, an industry trade association in Austin, said his group learned of the flaw only in the past