Operations security

Operations security (OPSEC) is an analytic process used to deny an adversary information - generally unclassified - concerning friendly intentions and capabilities by identifying, controlling, and protecting indicators associated with planning processes or operations. OPSEC does not replace other security disciplines - it supplements them.

OPSEC helps people identify the indicators that are giving away information about missions, activities, and operations. What do people observe about your schedule? What do you do when you go to work? What are you revealing by your predictable routines and the way you do business - these are indicators.

Source: U.S. Government OPSEC site