Internal crime includes the theft of objects such as raw materials, finished products, cash, and tools; the theft of information; and fraud. Employees also steal time by coming in late, taking long lunches, and attending to personal business during work hours. Most corporations put their resources into catching thieves rather than into preventing theft. However, the goal of a security system should be prevention. The company should first establish a code of ethics that applies to everyone. It should next assess its operations to determine where it is most vulnerable. Many companies screen potential employees with background checks, polygraph tests, and similar measures, although some security experts question the usefulness and reliability of these methods. Physical controls should include separating the shipping area from the receiving area, using closed circuit television to monitor sales clerks, and putting serial numbers on equipment. Procedural controls should focus on separating the access and control of any item, service, or piece of information among employees. In addition, employees should rotate from one operation to another. Companies should also insist that employees take vacations and should be suspicious if a worker refuses promotion. Signs of potential theft include paperwork that is either redone or often lost and repeated shortages of materials. Companies should also examine customer complaints carefully, since they may indicate internal crime.