Wednesday, January 20, 2016

GPS Jamming

Thanks to Laurie Thomas of Maritime Security/MTSA News for pointing me at a Coast Guard blog post about a safety alert the Coast Guard has issued about outages of the GPS navigation system. The safety alert describes a GPS outage noted recently at a ‘non-US port’ that covered a significant area of that port and surrounding ocean.

The Coast Guard is obviously concerned with outages like this being a hazard to navigation and that is the point of their alert. Other users of the GPS navigation system should also be similarly concerned. More important to readers of this blog are the potential effects of these types of outages could have on SCADA systems that use the GPS for control system timing.

The Safety Alert does not characterize this particular outage as either natural or man-made. From the point of view of the Coast Guard, this apparently isn’t really important as either would have similar effects on navigation. That is probably short sighted as someone that deliberately jams GPS signals over this large an area is probably intending to use that disruption to have other, more serious effects on maritime traffic.

In many ways industrial control system owners should follow the general guidelines in the Safety Advisory. They need to have in place plans for using alternative methods of timing synchronization during local GPS outages. More importantly they need to think about the potential security implications for such outages as they may signal an attempt to disrupt or gain access to remote SCADA installations as part of an attack on the ICS network.

NOTE: I have commented elsewhere that it would have been more helpful if the Coast Guard had characterized the reported outage as either man-made or natural. If natural it is a clear reminder that satellite communications of all sorts can be disrupted by geomagnetic storms. If man-made it is a clear declaration that at least one attacker has shown the ability and willingness to use wide spread GPS jamming with a certain level of immunity.

1 comment:

Jake Brodsky said...

When I chose to set up an internal GPS-based time sync system for our SCADA system, I chose three geographically diverse sites, and one of them has a disciplined hold-over oscillator in case none of the other sites can copy the time.

Also, a secondary time source to a LF radio station such as WWVB is a good idea. While it is possible to jam GPS locally from an aircraft quite easily, It is very hard to jam the WWVB signal over a wide area without being discovered. Antenna size and efficiency is a big deal.

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