1. Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, USA
2. Department of Computer Science and Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA

Correspondence to: Albert-László Barabási¹ Correspondence and requests for materials should be addressed to A.-L.B. (e-mail: Email: alb@nd.edu).

Abstract

Reliable communication on the Internet is guaranteed by a standard set of protocols, used by all computers¹. Here we show that these protocols can be exploited to compute with the communication infrastructure, transforming the Internet into a distributed computer in which servers unwittingly perform computation on behalf of a remote node. In this model, which we call 'parasitic computing', one machine forces target computers to solve a piece of a complex computational problem merely by engaging them in standard communication. Consequently, the target computers are unaware that they have performed computation for the benefit of a commanding node. As experimental evidence of the principle of parasitic computing, we harness the power of several web servers across the globe, which—unknown to them—work together to solve an NP complete problem².