I. Introduction
Online social networks (OSNs) such as Twitter and Facebook have become an important part of people's daily lives. OSNs not only help people stay in touch with family and friends, but also keep abreast of breaking news and emerging contents. False or unverified information spreads just like accurate information on the web, thus possibly going viral and influencing the public opinion and its decisions [1]–[4]. Especially, information cascades are identified as a major factor in almost every disastrous social network phenomenon, ranging from viral marketing, rumor diffusion, cyber violence, and various negative information spread. During the COVID-19 outbreak in early 2020, various kinds of bad information on the Internet, such as “a certain place closed the city”, “a certain place has a large-scale infection”, etc., greatly misled the public and disrupted public order [5]. Therefore, effective methods for restraining negative information cascades are crucial for OSNs and it has been a hot topic in the last decades.