Building on Clues: Examining Successes and Failures in Detecting U.S. Terrorist Plots, 1999-2009

Since 2001, the intelligence community has sought methods to improve the process for uncovering and thwarting domestic terrorist plots before they occur. Vital to these efforts are the more than 17,000 state and local U.S. law enforcement agencies whose role in the counterterrorism process has become increasingly recognized. As part of an on-going study for the Institute for Homeland Security Solutions (IHSS), this report examines open-source material on 86 foiled and executed terrorist plots against U.S. targets from 1999 to 2009 to determine the types of information and activities that led to (or could have led to) their discovery. Our findings provide law enforcement, homeland security officials, and policy makers with an improved understanding of the types of clues and methods that should be emphasized to more reliably prevent terrorist attacks, including the need to:

• Recognize the importance of law enforcement and public vigilance in thwarting terror attacks. More than 80% of foiled terrorist plots were discovered via observations from law enforcement or the general public. Tips included reports of plots as well as reports of suspicious activity, such as pre-operational surveillance, para-military training, smuggling activities, and the discovery of suspicious documents.
• Continue to investigate Al Qaeda and Allied Movements (AQAM), but do not overlook other groups, and pay particular attention to plots by “lone wolves.” Less
• than half of U.S. terror plots examined had links to AQAM, and many non-AQAM plots, primarily those with white supremacist or anti-government/militia ties, rivaled AQAM plots in important ways. Additionally, plots by single actors (“lone wolves”) have proven particularly successful, reaching execution nearly twice as often as plots by groups.
• Ensure processes and training are in place that enable law enforcement personnel to identify terrorist activity during routine criminal investigations. Almost one in five plots were foiled “accidentally” during investigations into seemingly unrelated crimes.Training is needed to recognize when ordinary crimes may be connected to terrorism.
• Work to establish good relations with local communities and avoid tactics that might alienate them. Approximately 40% of plots were thwarted as a result of tips from the public and informants. Establishing trust with persons in or near radical movements is jeopardized by tactics such as racial, ethnic, religious, or ideological profiling.
• Support “quality assurance” processes to ensure initial clues are properly pursued and findings shared. Investigating leads and sharing information across agencies led to foiling the vast majority of terrorist plots in our sample. Similarly, breakdowns in these basic processes led to lost opportunities to thwart some of the worst attacks, including 9/11.
• Expand the federal standards for categorizing suspicious activity reports (SARs). A large majority of the initial clue types we identified, including public and informant tips, as well as law enforcement observations made during routine criminal investigations, are only indirectly referenced in the current national SAR standards. Expanding them would enable more comprehensive reporting and greater information sharing of potential terrorist activity.

The Institute for Homeland Security Solutions (IHSS) is a research consortium established to conduct applied research in the social and behavioral sciences to address a wide range of homeland security challenges.