By Bob Brewin
JANUARY 17, 2003
http://www.computerworld.com/mobiletopics/mobile/technology/story/0,10801,77702,00.html?f=x596
Government officials and communications experts are assessing the public
safety and security implications of a newly posted online article that
provides directions for making cheap devices that can jam Global
Positioning System (GPS) signals.
Information in the article that appears in the current issue of the online
hacker magazine Phrack potentially puts at risk GPS devices used for
commercial navigation and military operations, authorities said.
The Phrack article (Volume 0x0b, Issue 0x3c, Phile #0x0d
http://www.phrack-dont-give-a-shit-about-dmca.org/archives/phrack60.tar.gz)
provides a detailed guide to building a low-cost, portable GPS jammer out
of components that can be easily obtained from electronics supply houses.
According to the article, the onslaught of cheap GPS-based navigation (or
hidden tracking devices) has made it necessary for the average citizen to
take up the fine art of electronic warfare. Electronics and GPS experts
who read the article this week called it technically competent and said
amateurs with a certain amount of technical skill could build a GPS jammer
from the plans.
Although the article said the jammer is designed to work only against
civil-use GPS signals broadcast on the frequency of 1575.42 MHz and not the
military frequency of 1227.6 MHz, James Hasik, an Atlanta-based consultant
and author of the book The Precision Revolution: GPS and the Future of
Aerial Warfare, disagreed.
Hasik said that while the Phrack jammer is targeted at civil GPS signals,
known as the C/A code, it could also threaten military systems, since
almost all military GPS receivers must first acquire the C/A signal
before locking onto the military signal, known as the P(Y) code.
Hasik said that GPS receivers are especially vulnerable to jamming because
of low signal strength after traveling through space from GPS satellites
orbiting 12,000 miles above the earth.
The U.S. Department of Defense, which faces the possibility of having its
GPS-guided weapons come up against Russian-made GPS jammers in Iraq, has
antijamming technology at its disposal. Still, Defense officials viewed the
Phrack article with concern.
Air Force Lt. Col. Ken. McClellan, a Pentagon spokesman, said the
implications of homemade jammers described in the article are somewhat
serious because the use of such jammers could disrupt commercial operations.
McClellan said GPS experts at the Pentagon do not at the moment view
homemade jammers as a hazard to flight safety for commercial aircraft or
ship operations, but rather a nuisance.
The Federal Aviation Administration is developing a nationwide GPS-based
precision landing system. And the Coast Guard operates a GPS-based maritime
navigation system on both coasts, the Great Lakes, inland waterways and
Hawaii. Bill Mosley, a spokesman for the Department of Transportation, the
parent agency of the FAA and the Coast Guard, said his department is well
aware of the threat posed by GPS jammers.
The DOT's John A. Volpe Transportation Systems Center, in Cambridge, Mass.,
prepared a report in August 2001 that said, Some jamming
devices/techniques are available on the Internet and proliferation will
continue, because a single device that could disrupt military and civil
operations worldwide would be attractive to malicious governments and groups.
As a result of that study, Mosley said, Transportation Secretary Norman
Mineta last March ordered an action plan to protect civilian GPS signals
and users by, among other things, the transfer of appropriate antijam
technology from the military to civil use. Mosley was unable say whether
that technology transfer has occurred.
Richard Langley, a GPS expert and professor of geodesy at the University of
New Brunswick in Fredericton, New Brunswick, called the implications of
home-brew GPS jammers scary. But he expressed doubt that the Phrack
jammer would be very effective against aircraft when used from the ground.
However, Langley noted that if a terrorist used the jammer from on board an
aircraft, it would extend the range and hence the effectiveness of the
jammer.
James Miller, program manager for GPS at United Air Lines Inc., said the
loss of a GPS signal in a commercial aircraft wouldn't cause a
catastrophic event, because airliners operate with multiple navigation
systems. But loss of a GPS signal by general aviation aircraft flying
solely on GPS could be quite challenging, he said.
Warren Morningstar, a spokesman for the Aircraft Owners and Pilots
Association in Frederick, Md., said general aviation pilots don't use GPS
as their sole navigation source and called the potential of jamming a
nuisance rather than a safety hazard.
You need to take it seriously anytime there is publicity about things that
could disrupt the critical infrastructure, said Mike Swiek,
