Two teens were suspected of breaking into U.S. computers.
Federal secrecy hampers the search for safeguards.
It was early morning on the first Monday in February when analysts at the Air Force's national computer monitoring center here started seeing an unusual series of red warning flags pop up on their screens, indicating unauthorized intrusions into about half a dozen electronic networks around the country. The analysts had become accustomed to spotting hundreds of suspicious entries a day into Air Force systems, but these were different. They followed a pattern. They appeared to be coming first from Harvard University, and later from other educational institutions in Utah and Texas, entering unclassified networks by exploiting a vulnerability in the Solaris operating system widely used at defense installations. Normally, there wouldn't be any correlations right away, but these connections seemed to be going to the same places and using the same techniques.