For Western lawyers working in China, doing business can require a curious combination of legal skills and 007-like stealth. Leave your laptop in your hotel room? Expect it to be searched. Call up a website to check the weather? You might load code that pulls data off your hard disk. Does your PC weigh more than it did when you left the States? That could be a homing device, implanted on the sly and now transmitting information about the merger your client is planning. It might sound like stuff from a James Bond movie. But the threats are real, say law firm technology chiefs—and worrisome.