#808: Dual Definitions of Discernible Damage
"Hezek she'eino nikar lo shmei hezek" (damage that is not discernible is not considered damage) according to halachah. A person who causes damage b’shogeg (accidentally) is exempt from liability if the damage is not noticeable. If, however, it was done b'meizid (deliberately), a k'nas (monetary penalty) is imposed as a deterrent to damaging the property of others.
Even though batei din (Rabbinical courts) don’t usually impose monetary penalties in current times (unless strictly required by halachah), the majority of latter-day poskim maintain that in the case of deliberate damage to another’s property it is proper for a Beis Din to enforce a fine.
Some examples that fall into the category of hezek she’eino nikar: the hezek caused by a metameh—someone’s possessions become tamei (ritually impure) due to the inattention of another, or the hezek caused by a menasech—wine belonging to another is mixed inadvertently with wine that was poured for avoda zarah (idol worship), making it forbidden.
And a contemporary example considered inadvertent hezek by some later authorities: A mistake occurs in the kitchen when a guest uses a treif (non-kosher) utensil in the host’s pot that has hot food in it, making the food and pot treif. The guest would not be responsible to cover the cost of the food or the pot (if it can’t be kashered).
However, the exact definition of hezek she'eino nikar is a matter of dispute among poskim. Some perceive the harm from the point of view of the end-product: is the damage obvious after the fact? If not, they posit, it is hezek she'eino nikar. This would be so even if the mazik (one inflicting damage) objectively handled the object detrimentally. Others define damage by the activity of the mazik—would it be obvious to onlookers that their actions are causing damage? If not, it is hezek she'eino nikar—even if the object is determined to be “changed” in some way.
A classic example of this machlokes: A person is observed putting his fellow's food under a bed. The food is then rendered inedible because someone was sleeping there and caused it to become impure.* No physical change to the item can be discerned. Depending on which interpretation of hezek sheino nikar is employed determines whether the mover of the food is liable. According to the first definition, there is no noticeable damage, so the owner of the food is not reimbursed by the mazik; but in lieu of the latter explanation, the act of placing the food under the bed was observed as damaging and the mazik must pay for the loss.
Clearly, if one person deletes files from another's computer or infects it with a virus, even unknowingly, it is considered noticeable damage, and the mazik would be held liable. This is similar to the case where one person puts poison in another’s cup by mistake; even though the damage is not visible (or, in the case of an electronic device, it is not tangible), it's quite evident that there is discernable change to the detriment of the original object.
(If the mazik poisons one cup among many cups, and it cannot be ascertained which cup is now tainted, the loss of available drink in the other cups would be categorized hezek sheino nikar and the mazik would only be liable for the costs associated with a single beverage.)
*Whether food that was left beneath a sleeping person is rendered unusable after the fact (or not) is a discussion beyond the scope of this halachah.