Worm

A worm is a form of malware - the earliest form conceived in the abstract, actually. In theory, a worm is not necessarily harmful (and, in fact, the first actual worm was intended to be entirely beneficial - see below).

It differs from viruses in that a virus is an addition to an existing (usually harmless, and productive) piece of binary software, whereas a worm is a complete, independent, stand-alone binary program. Worms typically replicate themselves through a data network.

They were first hypothesized in John Brunner's 1975 novel, "The Shockwave Rider". Worm-like software existed fairly early once data networks existed, but the first serious work with actual worms was done at Xerox PARC, in the late 1970's, on their in-house PUP internet. One interesting incident was when an error (in copying or transmission) caused one to spread out of control, crashing machines that it spread to; most of the Altos in the building were left crashed as a result.

Those worms were mostly productive; the first widespread non-productive (although not actually destructive) worm was the so-called Morris worm, released on the Internet in November, 1988. It spread through Sun-3 systems, and VAX computers running BSD UNIX; it was mostly an un-intended DoS attack, caused by its un-controlled replication.

External links

• John F. Shoch, Jon A. Hupp, The "Worm" Programs: Early Experience with a Distributed Computation, Communications of the ACM, Volume 25, Number 3, March 1982
• Eugene H. Spafford, The Internet Worm Incident Purdue Technical Report CSD-TR-933, September, 1991
• Eugene H. Spafford, The Internet Worm Program: An Analysis, Purdue Technical Report CSD-TR-823, November 1988
• Viruses, Worms, and Trojan Horses - a good but high-level overview