Why use your own computer when you can make use of other people's? Researchers at the University of Notre Dame in Indiana have demonstrated 'parasitic' computing — using other people's servers to do your own processing — according to an article in this week's Nature magazine.

The process is similar to that used by the likes of SETI@home (Search for Extraterrestrial Intelligence), which uses the processing power of millions of desktop PCs to scan data from a radio telescope in the hope of finding signs of life in outer space, says Nature.

The difference with parasitic computing is that the Notre Dame researchers did not ask for permission from the server owners. However, they did not have to hack to gain direct access to anyone's computer, but used the infrastructure of the internet itself to create a virtual machine.

Researchers Albert-Lásló Barabási, Vincent Freeh, Hawoong Jeong and Jay Brockman hijacked the infrastructure to show what is possible using the internet, said Nature.

A data validation program called a checksum is used, which runs on the transmission control protocol (TCP) connection between internet-connected computers. It forces the connected web servers to solve a specific mathematical problem, the researchers said.

The protocols are in place to ensure reliable communication but they can be exploited to compute with the communication infrastructure, turning the internet into a distributed computer. Servers will then unwittingly perform computation on behalf of an uninvited user, solving complex computational problems when they engage in standard communication and without being aware they are doing so.

In the event, it was more difficult and more time-consuming to process the information this way than to use the University's own computers, the researchers said, but the experiment shows interesting possibilities for using the internet, and raises important ethical questions about the use of other people's computers.