At Wired:

“We keep wiping it off, and it keeps coming back,” says a source familiar with the network infection, one of three that told Danger Room about the virus. “We think it’s benign. But we just don’t know.”

Military network security specialists aren’t sure whether the virus and its so-called “keylogger” payload were introduced intentionally or by accident; it may be a common piece of malware that just happened to make its way into these sensitive networks. The specialists don’t know exactly how far the virus has spread. But they’re sure that the infection has hit both classified and unclassified machines at Creech. That raises the possibility, at least, that secret data may have been captured by the keylogger, and then transmitted over the public internet to someone outside the military chain of command.