From laptops to refrigerators, some 17 billion household gadgets worldwide are linked to the Internet. As part of the Internet of Things, or IoT, they're meant to make life more convenient. They include air conditioners and vacuum cleaners controlled remotely by smartphone and webcams to keep an eye on pets and children. But there's a hidden risk. Increasingly, cybercriminals are using the devices to peer into people's lives. Who are the culprits and what are their motives? We delve into the dark side of the Web to find out.