Abstract: Anti-tamper device for protecting a lock box or another locking devices comprises a three-dimensional enclosure securely fastened to a bottom plate. The latter is adapted to be firmly attached to a vertical wall. First and second obstructing panels are located in the enclosure. The first obstructing panel extends from the top of the enclosure at the entrance of it. The second obstructing panel is parallel to the first obstructing panel and extends from the bottom plate. Between the extensions of the first and second obstruction panels, a passage is formed. This passage is so dimensioned so as: 1. To let the insertion of a hand with a key in it, only; 2. To render impossible, from the exterior of the enclosure to see a lock box or other locking device, disposed behind the second obstructing panel; and 3. To render unsuccessfully any attempt to damage the locks of a lock box or another locking device by using a straight tool.