Information Warfare has emerged as a key joint warfighting mission area.  The explosive proliferation of of information-based technology significantly impacts warfighting across all phases, the range of military operations, and all levels of war.

Some modern computer systems are subject to \“infection\” of their programs by reproducing computer viruses.  While it has been shown that detecting such a virus in general is an undecidable problem, there may be large classes of viruses against which effective defenses can be made.  Before an examination of the defenses is possible, a more complete catalog of the capabilities of viruses is necessary in order to determine if such classes exist.