Mobile mesoscale robotic device
Malicious mobile robotic microscale devices
Malicious parties could create airborne pollen sized ships (dozens of microns - needed for computing power to do some hacking) which try to find diamondoid atomically precise products and then try to disassemble their microcomponents for whatever reason. This attack only works well if the attacked products are made out of microcomponents that is they are non-monolothic. It would be bad if recyclability gets sacrificed only to defend against this.
As we know from tree pollen, particles as big as several tens of micrometers can be highly mobile in air and today’s average houses let plenty of them leak in even if all windows and doors are closed. So one can't avoid such an attack by going indoors in conventionally built houses. Also usually one don't want to be forced to go through airlocks all the time and AP products shouldn’t be confined to indoor use only.
One way to defend against such attacks may be to use hierarchical locking that converges to some combination lock stones (locking mechanisms). The size of the protection code must be sufficiently big or else there must be very view such stones since in the size of such an attacking particle fits a pretty powerful diamondoid atomically precise computer thus a massively parallel brute force coordinated random trial attack may be possible if the concentration of attacking miniature-ships is big enough. Even with a physical enforced delay between unlocking tests a too weak protection may be broken quickly.
To speed up their operation they may use air to self replicate (making them molecular assemblers of a bad kind) or use the victim structures micro-components for themselves if they fit or tap some energy that might be stored in the victim-structure.
[todo: can this be used for spam?]