Hackers have broken into some of the world's most powerful computer clusters in recent weeks in an apparently coordinated cyberattack targeting research and academic institutions.

Although officials sought Wednesday to play down the seriousness of the threats, some security experts warned that such a break-in could potentially enable a serious attack on the Internet.

Stanford University, the San Diego Supercomputer Center and the University of Illinois' National Center for Supercomputing Applications were among the systems hit.

Also affected was TeraGrid, a government-funded effort to link together several supercomputers, including those at San Diego and NCSA, so scientists can better crunch data for weather forecasting, astronomy and medicine. edition.cnn.com