Researchers have found a way to block the spread of self-propagating worms on corporate networks while keeping infected machines online so they can continue performing their legitimate duties. Using an algorithm they devised, the research team, based at Pennsylvania State University, can quickly measure how virulent worms are and halt their spread while keeping the false-positive rate less than 5 percent, said Peng Liu, an associate professor of information sciences and technology at PSU who is on the team.