China's main spy agency, the Ministry of State Security – or MSS – is now the largest and most active spy agency in the world. Its top target is not a foreign power, although the United States ranks number two. Instead, the priority for the MSS is China's own people, including those living abroad in the U.S.According to Jim Lewis, a former U.S. diplomat whose direct experience with China's intelligence agencies spans more than 30 years, Chinese nationals on foreign soil pose a unique risk to Chinese President Xi Jinping's regime."They could be plotting. It's happened before," Lewis said. "They could be agents of the evil foreign power. They could be learning something that Xi doesn't want them to learn. And so, they are seen as a risk, not as a threat, but as a risk."Spying on Chinese nationals in the U.S.According to Lewis, the MSS spies on Chinese nationals living abroad in a few ways. First, it surveils WeChat, a Chinese instant messaging and social media app used by more than 1 billion people worldwide."It's hard to do things in China without access to it," Lewis said. "And it's completely monitored with the cooperation of the owner by the Chinese state."In addition to monitoring online activity, Lewis told 60 Minutes that Chinese intelligence agents have also infiltrated college campuses in the U.S. This corroborates a report this month from the Stanford Review, which alleges that spies from the Chinese Communist Party are recruiting students at the California campus."I've had Chinese students tell me, 'I couldn't talk in class because the fellow sitting over there in the corner would report back.'"How China's MSS recruits its spies in the U.S.According to Lewis, China's MSS uses many of the same techniques as other spy agencies: sex, money, and revenge."You're a disgruntled employee. You haven't been recognized, and someone comes along and flatters you and says you can pay them back," Lewis explained.He also said the "honeypot" or "honey trap" strategy is common. A mainstay in spy activity for centuries, a honey trap is when an undercover operative, typically a woman, establishes a romantic or sexual relationship with someone to extract confidential information from them.If those do not work, there is always a monetary incentive. "Money works like a charm," Lewis said.The MSS last year released a propaganda video on China's largest social network, boasting that the agency "fights against evil." The video served as both propaganda and as a recruiting commercial."It's both an advertisement to recruit people and it's an advertisement to warn people that if you fall afoul of us, we will come after you," Lewis explained. "The Chinese want to give this perception they are largely present everywhere anymore."China's MSS is not the only agency sending a message through flashy videos. The CIA this month released its own videos to encourage Chinese nationals to spy for the U.S. Last year, the CIA also published a text-based video in Chinese that provided detailed, step-by-step guidance on how to safely get in touch with the agency online.A U.S. official told the New York Times that the agency released this month's videos because the instructional video was successful. The recent, highly produced videos tap into the fear of the Chinese Communist Party, especially for those who still have family living in China.Lewis told 60 Minutes that Chinese intelligence agents coerce Chinese nationals abroad by threatening to harm their family members back home in China."The ability to blackmail people into being agents because of threats to their family is very powerful, and it's a tool denied to the West," he said. "But it's a tool that the Chinese are not at all bashful about using."Lewis told 60 Minutes that people with ties to China are not the only ones who should care about Beijing's coercion abroad."One of the precedents that I thought we had learned in the 1940s is that countries that don't respect their own citizens, don't respect their neighbors," he said. "Fundamental rights are the basis of international security... Because when they mistreat their own citizens, you're next."The video above was produced by Brit McCandless Farmer and edited by Scott Rosann.