There is a new threat gathering online, one we are largely unprepared to meet. Until now, the story of the Internet wars has been a tale of escalating software. Shadowy criminals (or bored teenagers) design code which infects a computer, or spits out spam, or seeks out credit card numbers. They get better and better. Our protectors, meanwhile, struggle to keep up, designing programs that build protective walls around our computers, and filter the lottery notifications and Nigerian petroleum appeals from our inbox. But the crucial ingredient of a novel form of attack, recently detailed by computer scientists in California, is not software, but people. Large and growing numbers of mercenaries are being hired to help twist the landscape of social media -  to write rave reviews of products, post convincing spam, set up accounts on social networks, or perform other tasks. This gives their employers new ways to do everything from legally questionable marketing to outright theft There is a new threat gathering online, one we are unprepared to meet.