The federal government received numerous tips that drug dealer David Headley was inclined toward violent, radical Islam, yet continued to employ him as an informant in Pakistan. Headley went on to help plan the 2008 Mumbai attacks. It seems like the feds are always ignoring useful terrorism leads. Just how many of these tips do they get?

Thousands per day. The FBI’s Internet tip line, which handles both terrorism and domestic crime reports, has received an average of more than 700 messages per day since it was set up after September 11, 2001. But that doesn’t come close to representing the total number of tips the government gets, since many leads come from people walking into U.S. embassies, pulling aside police officers, or calling state and local hotlines. Plus, the staggering volume of information that counterterrorism analysts have to deal with includes not only direct tips, but also wire intercepts and leads from paid informants. When you add all that up, National Counterterrorism Center director Michael Leiter says the agency receives between 8,000 and 10,000 pieces of information per day, fingering just as many different people as potential threats. They also get information about 40 supposed plots against the United States or its allies daily. (Those numbers don’t include vague accusations about individuals becoming radicalized or activity inside Iraq and Afghanistan.)

The Headley case demonstrates the variety of ways in which tips get into the U.S. counterterrorism network. Several different people warned the government about Headley, but not every warning started in the same place. One tipster called an FBI tip line, another made a direct report to New York FBI officials, and two more contacted U.S. embassies overseas.

Government analysts must work quickly to find the sprinkling of serious threats in a sea of innocent misunderstandings and bogus tips . In some cases, the agents will decide that a given source is too biased to be believed. That’s what happened with Headley—analysts attributed the warnings about him to the bitterness of ex-wives and jilted lovers. It’s also difficult to separate out ordinary crimes from terrorist plots. For example, if someone reports a cut fence around a power plant, is that the work of a jihadist sleeper cell or a group of teenage vandals?

Even if a tip is deemed credible, the government may not have the resources to assign a team of agents to the suspect. Instead, the counterterrorism agencies try to focus on patterns. The FBI loads tips into the eGuardian system and checks for similar bits of information from other sources. The system also permits national, state, and local law-enforcement agencies to look up the name of a suspect or information about a particular plot. Classified information goes into a separate, more restricted system.

All of this means that first-time suspects and isolated pieces of information are less likely to be exhaustively investigated. That’s what happened with underwear bomber Umar Farouk Abdulmutallab. Intelligence agencies had heard that a Nigerian was training with al-Qaeda, received information about a Christmas plot, and read a couple of intercepts about someone named Umar Farouk (no last name) before Abdulmutallab’s father walked into a U.S. embassy to report him. No one ever figured out that these seemingly unrelated pieces of intelligence referred to the same plot, so intelligence agencies didn’t pour enough resources into investigating it.

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Explainer thanks Rick Nelson of the Center for Strategic and International Studies.

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