This type of question leads to what is known as Counter Intelligence. John Nolan defines Counter Intelligence as active measures undertaken to identify and neutralize the information collection activities of business rivals. First, the organization must define what it is which needs to be protected. This is not the same as theft, break-ins, or illegal activity that is handled by security.
Information is the resource that requires protection.
Second, the Counter Intelligence assesses the competitor's Intelligence capabilities. In other words, becoming familiar with the information resources and collection techniques the competitor utilizes to gain information. Communicating with distributors and suppliers who also contact the competitor is one method of learning what the competitor is up to. The Counter Intelligence should view their own company as if they were the competitor. Third, test the organization's vulnerability to the collection method that the competitor is believed to use.