With the arrests last week of 24 alleged terrorists in Britain, the government's legal tools for fighting Al Qaeda are up for debate once again. Homeland Security Secretary Michael Chertoff suggests that Congress emulate Britain's law allowing extended pretrial detention of suspects. Others have observed that British law enforcement can more easily initiate investigations and obtain search warrants than their American counterparts.

Visiting Scholar John Yoo

But increasing detention time or making warrants easier to come by merely extends an old-fashioned approach to catching terrorists. These tools require individualized suspicion and "probable cause"; police must have evidence of criminal activity in hand. Such methods did not prevent 9/11, and stopping terrorists, who may have no criminal record, requires something more.

Instead of enlarging the scope of standard law enforcement methods, we should be doing what Americans do best--innovating and applying new technology to the problem. Despite what civil libertarians might have you think, that means data mining.

Data mining uses supercomputers to analyze vast amounts of information for suspicious patterns of behavior. It appears to have been an important tool in breaking up the plot in Britain. According to news reports, British authorities searched telephone, e-mail and banking records and uncovered connections between the bombers in Britain and their supporters in Pakistan.

American efforts to develop sophisticated data-mining abilities died early in 2003, when criticism killed the Defense Department's Total Information Awareness program. The idea was to develop mining techniques to compare information in government and commercial databases. Civil libertarians engaged in a scare campaign representing the TIA as an unchecked Big Brother. Congress cut off all funding for the program. It was a political defeat early in the war on terrorism, and the president retreated as fast as he could.

But that was a dangerous overreaction. Corporations already use data mining to detect consumer fraud and to market products such as credit cards and magazine subscriptions. Financial companies analyze patterns that might indicate a stolen credit card or bank account number. Why should the government be barred from using similar tools on similar databases to protect the country from attack? Data mining is nothing but an ordinary, ubiquitous feature of technology today.

In fact, the government also already uses modest forms of data mining. In response to drug cartels and organized crime, federal authorities are allowed to search banking records for signs of money laundering. Such analysis has already paid off in the war against terror by identifying groups that funnel funds to extremist organizations.

What about privacy concerns? The Supreme Court has found that the information in business records does not merit 4th Amendment protection because the consumer has already voluntarily turned over the information to a third party.

Still, civil libertarians object to data mining because most of the records and communications that would be searched are innocent, and there is no suspicion of criminal activity attached to any individual whose records may be mined. When the National Security Agency was discovered in May to be looking at telephone billing information on millions of calls within the United States, Sen. Patrick Leahy (D-Vt.) railed at a hearing: "Are you telling me tens of millions of Americans are involved with Al Qaeda?"

But it's important to remember that data mining is not the same thing as gathering the information in the first place. The NSA's program of looking at billing information, for example, doesn't raise the same constitutional issues as its other recently revealed program: warrantless wiretaps. There, the content of communications was captured. A federal trial judge in Detroit enjoined such surveillance Thursday, in a decision already on appeal.

Data mining could be controlled and developed so that it protects us from terror and maintains our privacy. Analysis could be limited to data already turned over to third parties. Searches could be performed initially by computer; only after a certain level of suspicious activity had been registered would an intelligence or law enforcement officer be allowed to see the results. A warrant could still be required to investigate the content of communications or the purpose of purchases.

Right now, we're fighting terror with one hand behind our back by refusing to exploit data-mining tools. London's success should serve notice that we must use our technological sophistication and reject the sky-is-falling claims of the extreme civil libertarians.

John Yoo is a visiting scholar at AEI.