CI stands for counterintelligence and is the dark side of security.  It deals with preventing and apprehending those who want to steal your information or intellectual property.  In dealing with CI it is mainly spotting the behavior, traits and indicators of the perpetrators.

A good place to start in dealing with CI is the following:

Another aspect of CI especially for those of you that have security clearances are close and continuing contacts.  The following is a DOE explanation:

Finally as terrorism is on everyone’s mind, how can you spot someone planning a terrorist act?  Perhaps this will help: