The next time you find a hotel room with free Wi-Fi, you might not want to celebrate right away: your hotel could be selling your eyeballs to advertisers. When web developer Justin Watt stayed at the Courtyard Marriott hotel in Times Square, he discovered that the facility's wireless hotspot was injecting Javascript code into every webpage for the purpose of delivering ads. Then, with a little help, he traced the injection tool back to a wireless internet gateway company called RG Nets.

You've probably never heard of RG Nets, and we imagine that's the way the company would like it to stay, because RG Nets' website and marketing materials make it blatantly obvious that its products are designed to exploit users for the benefit of those that own the network. RG Nets proudly calls its hardware a "Revenue Extraction Gateway" and boasts about its ability to "exert total control over the end-user population." Here's how the company describes the feature that Justin Watt discovered, for instance:

Arbitrary HTML page rewriting enables the operator to inject static or dynamic advertising onto every web page the end-user views. When combined with a handful of simple rewriting recipes, interstitial advertising and even forced viewing of video content are easily attained.

Meanwhile, other parts of the website describe ways to selectively profile and throttle particular users in order to sell them a higher tier of internet service, and track them to target ads. It all sounds extremely shady, and not a business that a reputable hotel would necessarily want to be associated with, but we suppose it's their network, after all.

We're also not sure how widespread RG Nets' reach is, or how many hotels or other supposedly complimentary Wi-Fi hotspots are engaging in similar behavior right now, but there's a brisk business for software of this sort, generally speaking. Should the idea spread, you may not be able to assume that the price of your room pays for "free" internet in addition to the roof over your head.