Most savvy corporations already have strict policies about what employees can and cannot do at their workplace computers, but the stakes for not enforcing those policies and properly investigating misuse are rising.

In one recent case from New Jersey, a company was sued by the victim of child pornography that a worker had on his work computer. A judge initially threw out the suit, but an appeals court reinstated it—holding in a groundbreaking decision that an employer may have a duty to prevent a crime from being committed against a third party.

Seth Borden, an employment lawyer with Kreitzman Mortensen & Borden, ...