^ abIEEE Annals of the History of Computing, Volumes 27-28. IEEE Computer Society, 2005. 74. Retrieved from Google Books on 13 May 2011. "[...]from one machine to another led to experimentation with the Creeper program, which became the world's first computer worm: a computation that used the network to recreate itself on another node, and spread from node to node. The source code of creeper remains unknown."