Story highlights The virus has resisted multiple efforts to remove it from Creech's computers

It may be a common piece of malware

They're sure that the infection has hit both classified and unclassified machines

A computer virus has infected the cockpits of America's Predator and Reaper drones, logging pilots' every keystroke as they remotely fly missions over Afghanistan and other warzones.

The virus, first detected nearly two weeks ago by the military's Host-Based Security System , has not prevented pilots at Creech Air Force Base in Nevada from flying their missions overseas. Nor have there been any confirmed incidents of classified information being lost or sent to an outside source. But the virus has resisted multiple efforts to remove it from Creech's computers, network security specialists say. And the infection underscores the ongoing security risks in what has become the U.S. military's most important weapons system.

"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.

The lion's share of U.S. drone missions are flown by Air Force pilots stationed at Creech , a tiny outpost in the barren Nevada desert, 20 miles north of a state prison and adjacent to a one-story casino. In a nondescript building, down a largely unmarked hallway, is a series of rooms, each with a rack of servers and a "ground control station," or GCS. There, a drone pilot and a sensor operator sit in their flight suits in front of a series of screens. In the pilot's hand is the joystick, guiding the drone as it soars above Afghanistan, Iraq, or some other battlefield.

Some of the GCSs are classified secret, and used for conventional warzone surveillance duty. The GCSs handling more exotic operations are top secret. None of the remote cockpits are supposed to be connected to the public internet. Which means they are supposed to be largely immune to viruses and other network security threats.

Use of the drives is now severely restricted throughout the military. But the base at Creech was one of the exceptions, until the virus hit. Predator and Reaper crews use removable hard drives to load map updates and transport mission videos from one computer to another. The virus is believed to have spread through these removable drives. Drone units at other Air Force bases worldwide have now been ordered to stop their use.

In the meantime, technicians at Creech are trying to get the virus off the GCS machines. It has not been easy. At first, they followed removal instructions posted on the website of the Kaspersky security firm. "But the virus kept coming back," a source familiar with the infection says. Eventually, the technicians had to use a software tool called BCWipe to completely erase the GCS' internal hard drives. "That meant rebuilding them from scratch" -- a time-consuming effort.

The Air Force declined to comment directly on the virus. "We generally do not discuss specific vulnerabilities, threats, or responses to our computer networks, since that helps people looking to exploit or attack our systems to refine their approach," says Lt. Col. Tadd Sholtis, a spokesman for Air Combat Command, which oversees the drones and all other Air Force tactical aircraft. "We invest a lot in protecting and monitoring our systems to counter threats and ensure security, which includes a comprehensive response to viruses, worms, and other malware we discover."

However, insiders say that senior officers at Creech are being briefed daily on the virus.

"It's getting a lot of attention," the source says. "But no one's panicking. Yet."