As an example, the accounting department or accounting books can be locked up in a room or drawer. Only people having a need for the information should have a key. A variant of this procedure is used when out-sourcing. Companies that out-source various portions of their business often separate the confidential information among multiple vendors. No one vendor is given sufficient information to be able to recognize or use the confidential information.
Passwords are one method.
Separate computer systems are another. A computer system may give off a warning when someone tries breaking passwords, identifying both the problem and the computer terminal being used. Confidential information should be put away when not in use. A blanket may be thrown over a machine. A drawer may be closed and locked.