Please read the Defense Security Service's Suspicious Indicators and Security Countermeasures for Foreign Collection Activities Directed Against the US Defense Industry, dated 2008. This document is a list of indicators prepared by the Defense Security Service for identifying foreign intelligence entity (FIE) efforts to penetrate and/or steal defense industrial and classified information. These indicators are what would be incorporated, along with all other standard security practices (active and passive defensive counterintelligence) into a basic methodology used to detect FIE activity.
It is important to read and understand the types of indicators. These form the core of counterintelligence analysis for addressing threats against the defense supply chain, defense industry, military technology, etc.