Thaindian News

Bern, Aug 12 (IANS) Tracing the source of epidemics or crime has become much more complicated in the age of Internet connectivity, unlike detecting those committed by old, mafia-style criminal organisations but scientists are using mathematics to solve the problem.

Ecole Polytechnique Federale de Lausanne (EPFL) researcher Pedro Pinto of the Audiovisual Communications Lab and his colleagues have developed an algorithm that could help investigators, find the source of a crime or otherwise, as long as a network is involved.

“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,” said Pinto, reported journal Physical Review Letters.

Giving an example, he said: Suppose you come across a rumour about yourself that has spread on Facebook and been sent to 500 people - your friends, or even friends of your friends. How do you find the person who started the rumour?

“By looking at the messages received by just 15 of your friends and taking into account the time factor, our algorithm can trace the path of that information back and find the source,” Pinto adds.

This method can also be used to identify the origin of a spam message or a computer virus using only a limited number of sensors within the network.

Out in the real world, the algorithm can be employed to find the primary source of an infectious disease, such as cholera. “We tested our method with data on an epidemic in South Africa provided by EPFL professor Andrea Rinaldo’s Ecohydrology Laboratory,” says Pinto.

“By modelling water networks, river networks and human transport networks, we were able to find the spot where the first cases of infection appeared by monitoring only a small fraction of the villages.”

The method would also be useful in responding to terrorist attacks, such as the 1995 sarin gas attack in the Tokyo subway, in which poisonous gas released in the city’s subterranean tunnels killed 13 people and injured nearly 1,000.

“Using this algorithm, it wouldn’t be necessary to equip every station with detectors. A sample would be sufficient to rapidly identify the origin of the attack, and action could be taken before it spreads too far,” says Pinto.

Computer simulations of telephone conversations that could have occurred during the 9/11 terrorist attacks were used to test Pinto’s system.

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