From an article in newscientist magazine Last year, a man was arrested in London for accessing the internet via someone else's wireless connection. Now "borrowing" a stranger's Wi-Fi could become the norm, and might even be encouraged. Jon Crowcroft and Nishanth Sastry at the University of Cambridge have developed a "wireless cooperative" that allows people to share their Wi-Fi connection with strangers, securely and at no extra cost. It could enable cities to provide free, secure Wi-Fi coverage without needing to invest in expensive infrastructure. Despite many promises, ubiquitous wireless internet remains a distant dream in most places. Planned city-wide Wi-Fi projects in Dublin, Ireland, and in San Francisco have been derailed by the cost of blanketing a city in routers. And schemes that get people to open up and share their home routers with passers-by are "dangerous from a security perspective", Sastry says. If malicious users take advantage of free connections to launch viruses and spam, the router's owner could be held liable. Simple sharing also encourages freeloaders, who borrow other people's routers but don't share their own. Sastry claims to have come up with a scheme that is not only secure, but also prevents freeloading. To join, you download free software that turns your router into a hotspot and logs your username and router address with an online registry. If you are out and about and want to use a router belonging to another member of the co-op, you enter your username, which the router then checks against the central registry to confirm you are a member. The registry also sends your home router's address to the router you are borrowing. From then on you can surf the net normally via the borrowed Wi-Fi router. A system known as a secure tunnel routes all your data packets via your home router, so to the outside world that is where they appear to come from. "You will be traceable," Crowcroft says. "Liability for anything bad can follow through to you." As you can only join the cooperative if you register your wireless router, the freeloader problem is solved too. The Spanish company Fon already sells technology that allows people to share their Wi-Fi connections, but to use it you have to buy a special router. The co-op's open-source software means people can use the routers they already own. "It's a nice way to use existing resources to solve a community problem," says Bruce Schneier, a computer security expert based in Mountain View, California.