The Collaborative International Dictionary of English v.0.48:

Unprotected \Unprotected\
   See protected.

WordNet (r) 3.0 (2006):

unprotected
    adj 1: lacking protection or defense [ant: protected]

Moby Thesaurus II by Grady Ward, 1.0:

31 Moby Thesaurus words for "unprotected":
   aidless, bare-handed, defenseless, fatherless, friendless,
   guardless, guideless, helpless, insecure, leaderless, motherless,
   pregnable, unarmed, unarmored, unattended, uncovered, undefended,
   unfortified, unfriended, ungarrisoned, unguarded, unsafe,
   unscreened, unsheltered, unshielded, unsuspecting, untenable,
   unwarned, unwatched, vulnerable, weaponless