Werewolf

Werewolf is anti-personnel program from Scandinavan Bloc is refined version of Hellhound. It doesn't use the rather theatrical graphics of the conventional version, instead tracing the runner quietly with an Invisibility subroutine which prevents detection. Unless the target is using Seeya or makes a Very Difficult Awareness roll, he won't notice the Hellhound until its attacking him. The nickname for this extremely illegal program is Werewolf, since it hits when you when you least expect it.

Source

 * Rache Bartmoss Guide to the Net, pg.107
 * Rache Bartmoss' Brainware Blowout, pg.58