The NSA already knows how to find out where you're surfing from. Now, it wants to share its secret with online advertisers.

There are a couple of services that can match Internet Protocol, or IP, addresses to physical locations. But the technique isn't exactly iron-clad. Routing traffic through a server in some other country, for example, can throw these programs off the trail.

The NSA approach, "Network Geo-location Technology," is different, Military Information Technology magazine notes. It relies on latency, instead. By looking how long traffic on one computer takes to get to another, it can tell where that first PC is.

"The most common use of Internet geo-location technology is in the area of ad-serving. When users do a Google search, for example, the technology will show ads to them that are localized depending on their geographic location," the magazine says. "The technology is also used for on-line verification of identity. If a user is registering on-line to buy an airline ticket, for instance, and the user claims to be located in a certain place, the technology can determine whether that user is actually located there or in a different place and then either block the transaction or ask for additional verification."

The system is one of 44 technologies that the NSA is looking to sell off to businesses. Others include a "Shredder Residue Dispersion System" and an "Enhanced Beacon Recognition for Laser Communications."