United Natural Foods Inc one of the largest U.S. grocery distributors whose clients include Whole Foods, took certain systems offline in recent days after the discovery of unauthorized activity on internal networks,

A string of recent cyberattacks and data breaches involving the systems of major retailers have started affecting shoppers.

The bad news keeps coming for United Natural Foods Inc., as the food distributor followed the disclosure of an ongoing cyberattack by saying on Tuesday that the ending of a supply agreement would lead...