Subject: [NEXTEL-1] GPS data could stop wireless network attacks

From: [email-masked]
Date: Tue, 20 May 2003 23:09:07 -0400

GPS data could stop wireless network attacks 
 
May 20, 2003 
  
A new danger to wireless network security has been revealed by a team of US computer
researchers. A so-called "wormhole attack" could be used to knock a vulnerable network out
of action or defeat a wireless authentication system.

But the same researchers that discovered the threat have also devised a radical scheme
designed to counter it, involving tagging packets with GPS information or timestamps.

In a wormhole attack, an intruder would intercept wireless data packets traveling across
one part of a network and quickly re-insert them at another physical point on the network.

"Ad-hoc" wireless computer networks could be severely disrupted using the technique. These
operate by passing communications from one node to the next until they reach their
destination, rather than being controlled by a central server. Ad-hoc networks are used to
extend the range of wireless LAN networks, and are also used by the military and emergency
services. 

Open door 

Even if the network traffic is encrypted, an attacker would be able to control the data
flow across the network say Yi-Chin Hu and Adrian Perrig at Carnegie Mellon University,
Pennsylvania, and David Johnson at Rice University, Texas. If traffic is not encrypted, an
attacker could alter packets of information without detection.

Wireless authentication systems, including encrypted ones, could be duped using such
wormholes. By relaying the authentication communication using concealed transceivers, an
attacker could, for example, trick a door security system into opening, says Hu. 

"The wormhole puts the attacker in a very powerful position relative to other nodes in the
network," the researchers write. "Possible ways for the attacker to then exploit the
wormhole include discarding rather than forwarding all data packets, thereby creating a
permanent Denial of Service ... or selectively discarding or modifying certain data
packets."

Bruce Schneier, computer security expert and founder of US company Counterpane, says the
attack is elegant and could be highly effective. He says an attack would be tricky to pull
off but told New Scientist: "Experience tells me that someone will figure out how to make
it work."

Identity tag 

The researchers propose defending networks against the attack by attaching identifying
tags to each packet. Dubbed "packet leashes", these tags let each node on the network
determine where a packet has come from. 
  
They suggest tagging packets with GPS information or a timestamp based on a synchronized
network clock. Both could be used to verify that a packet genuinely comes from another
nearby node and not one intercepted much further away.

But the proposed countermeasures would be costly to implement, according to Schneier:
"They require accurate location or accurate absolute clock information - both are hard to
come by."

He suggests instead exchanging bits very rapidly between nodes and using the speed of
light to determine the genuine distance between these points on the network.

The threat and the countermeasure are outlined in the technical paper Packet Leashes: A
Defense Against Wormhole Attacks in Wireless Networks presented at the Twelfth World Wide
Web conference in Bucharest, Romania. 
 
Will Knight
 
http://www.newscientist.com/news/news.jsp?id=ns99993747

------------------------ Yahoo! Groups Sponsor ---------------------~-->
Get A Free Psychic Reading!
Your Online Answer To Life's Important Questions.
http://us.click.yahoo.com/aM1XQD/od7FAA/uetFAA/61FxlB/TM
---------------------------------------------------------------------~->

Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/