Private security is absolutely essential in many areas of the world where the capacity of public law enforcement and justice agencies, whether through lack of resources, expertise, or will are unable to meet the basic and specialized needs of public safety and national security. Private security can mean the difference between a failed state and a faltering one and a means of buying time for the maintenance and strengthening of key institutions. Where regulation and oversight are adequate, private security can be a valuable and reliable government partner. However, private security firms have shown themselves to be notably vulnerable to criminal and terrorist penetration. There are several consequences and effects of criminal penetration of private security, such as the undermining of citizen confidence in state institutions, the weakening of public security organizations, and the discouraging of alliances and international support. Even though these types of problems are being addressed, the vulnerability of private security businesses to terrorist penetration may prove just as challenging. This paper focuses on those private security establishments that were formed for the express purpose of criminality or terrorism using the cover of legitimate security firms, as well as those that otherwise turned to criminal or terrorist agendas. In addition, it focuses on the many disparate private security businesses and enterprises abroad, rather than the larger, regularized United States and Western firms that have been generally well-regulated. 59 footnotes