Pentagon researchers this month completed the first set of test data for the controversial Total Information Awareness system, a key technologist for the project says.

Lt. Col. Doug Dyer, a program manager at the Defense Advanced Research Projects Agency (Darpa), said at an IBM-sponsored conference on data privacy in Almaden, Calif., this week that Americans must trade some privacy for security. "Three thousand people died on 9/11. When you consider the potential effect of a terrorist attack against the privacy of an entire population, there has to be some trade-off," Dyer says.

Total Information Awareness, an experimental computer system being developed by Darpa under Vice Adm. John Poindexter, seeks to scan information about passport, visa, and work-permit applications, plus information about purchases of airline tickets, hotel rooms, over-the-counter drugs, and chemicals--both here and abroad--to discern "signature" patterns of terrorist behavior. Congressional leaders have criticized the system's potential to spy on Americans and agreed to restrict further research and development without consulting Congress.

Signals of potential terrorist activity are likely to be weak amid a field of data "noise," Dyer says. TIA is designed to seek patterns that could indicate terrorist behavior while preserving people's anonymity, he adds. "We're testing our hypothesis on nothing but synthetic data."

Total Information Awareness, the keystone project of Darpa's Information Awareness Office, incorporates language-translation, data-searching and pattern-recognition, and decision-support technologies, according to the project's Web site. According to Dyer, the system won't scan "irrelevant" personal information about Americans, such as medical records, but could consider records of over-the-counter drug purchases, which could indicate planning of a bioterrorist attack.

Dyer says the initial experiment data set, completed this month, could also consider relationships between purchases of certain chemicals, whether the buyer or a family member was involved in an activity such as farming that could explain a benign reason for the purchase, and where the purchase was made.