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 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.

] 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.

Classic Bill Joy moment here. The availability of that article is not what creates the risk associated with relying on GPS. Its the insecurity of the system that creates the risk. If that article was published in scientific american instead of phrack the wording of this article would be tremendously different.

Notice how the author goes around to different subject matter experts searching for someone who is willing to say "this is bad." Each expert says "this has no effect on my space, but it might cause problems in that space over there." The author then asks someone who works in that space, and is told the same thing over again. Basically, yes the authorities know this is a risk and they mitigate it like any other risk.