"communication infrastructure, transforming the Internet into a distributed computer in whichservers unwittingly perform computation on behalf of a remote node. In this model, which wecall `parasitic computing?; one machine forces target computers to solve a piece of a complexcomputational problem merely by engaging them in standard communication. Consequently, thetarget computers are unaware that they have performed computation for the beneÆt of acommanding node. As experimental evidence of the principle of parasitic computing, we harnessthe power of several web servers across the globe, which–unknown to them–work together tosolve an NP complete problem. 4 PROOF-OF-CONCEPTThe proof-of-concept demonstration reported by Barabasi et al. (2001) involved a single“parasite” computer networked to multiple “host” web servers by means of the Internet. Theunderlying communication between the parasite and hosts followed the standard TCP/IPprotocol. Within this context, the parasite exercised a form of covert exploitation of hostcomputing resources, covert because it was accomplished without knowledge or consent of hostowners, and exploitation because the targeted resources were used for purposes of interest to theparasite, not necessarily the host owners. Covert exploitation of networked computing resourcesis not a new phenomenon (Smith, 2000; Velasco, 2000). In this section, we will review a fewcommon examples of covert exploitation including some that take advantage of knownvulnerabilities in the Internet communication process.DEFINITIONA "parasite" computer attempts to solve a complex task by breaking it up into many smallcomponents and distributing the processing of these components to remote computers whichperform this processing without the knowledge or consent of those owning the remote computing 5 resources. This is achieved through the use of the TCP/IP Internet protocol and, in particular, thechecksum function of this protocol. After a discussion of similar exploits, the ethical issuesinvolved in this demonstration are analyzed. The authors argue that harm should be the standardfor determining if parasitic computing is unethical. They conclude that a revised notion of therights of ownership is needed when dealing with the shared nature of the Internet. Suggestionsfor future research are offered. Parasitic computing is a concept by which one can use the resources of machines that areconnected on the Internet. This technology exploits open Internet protocols to use the resourcesof remote machines. As the name suggests, the machine that requires the services of others doesnot need to be authorized by the latter. Any machine, which is connected to the Internet, has tocarry out minimum processing of any packet they receive without any authorization. Thisconcept is exploited by parasitic computing in order to make use of computing powers of remotemachines and web servers all around the globe. So one cannot really stop their machines frombeing utilized in this manner. Sending a message through the Internet is a sophisticated process regulated by layers ofcomplex protocols. For example, when a user selects a URL (uniform resource locator),requesting a web page, the browser opens a transmission control protocol (TCP) connection to aweb server. It then issues a hyper-text transmission protocol (HTTP) request over the TCPconnection. The TCP message is carried via the Internet protocol (IP), which might break themessage into several packages, that navigate independently through numerous routers betweensource and destination.When an HTTP request reaches its target web server, a response isreturned via the same TCP connection to the user's browser. The original message isreconstructed through a series of consecutive steps, involving IP and TCP; it is Ænallyinterpreted at the HTTP level, eliciting the appropriate response (such as sending the requestedweb page).Thus, even a seemingly simple request for a web page involves a signiÆcant amountof computation in the network and at the computers at the end points. The success of the Internetrests on the cooperation of and trusts between all involved parties. 6 "