Network sniffing algorithm could have fingered 9/11 suspects

A group of researchers has come up with a new algorithm that they say can be used to snoop information networks to trace rumor leaks, locate the source of disease epidemics, and even potentially stop terror attacks.

According to Pedro Pinto and colleagues at the Swiss Federal Institute of Technology in Lausanne (EPFL), the new technique can be used to trace the source of information within large-scale network systems given only very few data points.

"Using our method, we can find the source of all kinds of things circulating in a network just by 'listening' to a limited number of members of that network," Pinto explains in a press release.

The basic idea is to choose a few well-connected nodes on a network and use the time it takes a piece of information to reach each of those nodes to triangulate the information's source.

The research, which was published in the journal Physical Review Letters last Friday, is based on principles used by wireless carriers to pinpoint mobile phone users, but the boffins say it can be applied to a wide variety of networks, including online social networks or even real-world networks of people in villages and towns.

For example, the researchers applied the technique to data gathered from cholera outbreak that occurred in South Africa in 2000. After building a detailed model of the network of roads and waterways that could have spread the disease from village to village, Pinto and his team were able to use the new algorithm to locate the source of the epidemic with 90 per cent confidence, using data from just 5 per cent of the network nodes.

In another test, the boffins built a computer simulation of the telephone calls that could have occurred during the terrorist attacks on September 11, 2001.

"By reconstructing the message exchange inside the 9/11 terrorist network extracted from publicly released news, our system spit out the names of three potential suspects," Pinto says, "one of whom was found to be the mastermind of the attacks, according to the official enquiry."

If those use cases aren't juicy enough for you, the EPFL eggheads say the new technique could potentially have a wide variety of other applications, including tracing the origin of spam and computer viruses, or finding the sources of Facebook rumors.

And then there's always the old fallback: "It could also be a valuable tool for advertisers who use viral marketing strategies," the EPFL's press release helpfully points out. ®