Embassy closings spurred by al-Qaida threat circulating on secretive jihadi chat rooms

In secretive chat rooms and on encrypted Internet message boards, al-Qaida fighters have been planning and coordinating attacks, including a threatened plot that U.S. officials say closed 19 diplomatic posts across Africa and the Middle East for more than a week.

For years, extremists have used online forums to share information and drum up support, and over the past decade they have developed systems that blend encryption programs with anonymity software to hide their tracks. Experts say jihadist technology may now be so sophisticated that many communications avoid detection by National Security Agency programs that were designed to uncover terror plots.

One expert calls it a cat-and-mouse game between terrorist groups that can buy commercial technology and intelligence agencies that are trying to find ways to continue to monitor them.