Christmas Tree EXEC

The first widely publicised replicating network program was the Christmas Tree which paralysed the worldwide IBM VNet private electronic mail network on 17th December 1987.

Written by a student at the University of Clausthal-Zellerfield, West Germany in REXX, it drew a crude Christmas tree - then sent it to all the recipinet's email contacts. In this way it spread onto the European Academic Research Network (EARNet) then BitNet and onto IBM's world-wide VNet. Through all these systems it caused massive disruption.

Technically it is not regarded as a ‘worm’ because it needs the user to launch it - instead it is described as a Trojan Horse with a replicating property/

References

list of various "exotic" viruse and worms and early report [1] The full source code