ARTICLES :: "Who's Using Your Machine?" :: Wired


	ARTICLES By Publication :: By Date

PARASITIC COMPUTING

Who's Using Your Machine?

Wondering if your new Pentium 4-powered PC is moonlighting on the side? You should be. While your system is happily chomping away on 5 gigs of digital video, a freeloading interloper could be sucking excess processing power for its own dirty work.

Like a leech feeding off its host, a simple kernel of code can tap into your PC or Web server undetected, then use it to solve complex mathematical equations. The hack was devised by University of Notre Dame physicist Albert-Lászlò Barabási and computer scientists Jay Brockman and Vincent Freeh, along with Hawoong Jeong, a physicist from the Korea Advanced Institute of Science and Technology.

Such parasitic computing exploits the checksum - the error-detection scheme Net-connected computers perform on every data packet received to make certain it wasn't corrupted in transmission. The parasite covertly tucks bits of checksum data into each packet. As the host computer verifies this data with that of an arriving packet, it unwittingly crunches the equation embedded in the incoming checksum. When the checksum reports back to the sender, it carries with it a solution to the parasite's problem. Multiply this by hundreds of Web servers and networked PCs, and the Net could be doing a lot of people's busywork. "We could use all the idle resources on the Internet," says Jeong. "If this happens - and sooner or later it will - it means one really big supercomputer."

Sound familiar? It is. Parasitic computing works a lot like other forms of distributed computation (think Seti@home without user permission). Hackers can abuse parasitic code, but aside from slowing the network, they're not likely to do much damage, says Jeong. However, should a group need major tech muscle without a price tag, a parasitic assault may be the way to go. But Jon Howell, Microsoft Research computer scientist, warns:"Your problem must have a very high computation-to-communication ratio to be profitable." And if you don't want your hardware made slave to someone else's data crunching? The answer is simple: Unplug from the Net.