China has new set of restrictions on what citizens will be able to post on messaging applications, Chinese officials said Thursday. The new set of regulations is a national security measure, the officials said. Under the new policy, China is blocking two foreign chat apps, Kakaotalk and the wildly popular Line, saying that the messaging services were being used to ferry terrorist communications. And it is introducing a registration policy for all other messaging apps, including WeChat, which is very popular in China.