WordNet (r) 3.0 (2006):

furtiveness
    n 1: a disposition to be sly and stealthy and to do things
         surreptitiously [syn: furtiveness, sneakiness,
         stealthiness]

Moby Thesaurus II by Grady Ward, 1.0:

30 Moby Thesaurus words for "furtiveness":
   artfulness, clandestine behavior, clandestinity, covertness, craft,
   cunning, deceit, deceitfulness, duplicity, falseheartedness,
   falseness, guile, hypocrisy, indirection, insidiousness, prowl,
   prowling, shiftiness, slinkiness, slyness, sneak attack,
   sneakiness, stalking, stealth, stealthiness, surreptitiousness,
   treacherousness, underground activity, underhand dealing,
   underhandedness