Shadow IT can be used by one individual or a group of employees, which suggest two levels of use: an individual and collective use of shadow IT. The study takes a social influence perspective to investigate the mechanisms that underlie the dissemination process of shadow IT among users and uncover the reasons why they use shadow IT. We performed a survey among employees of four companies. The results show that the social influence varies depending on the group of reference in question (peer, superior, mass influence). We found that employees are strongly influenced by their peers and by a mass of people to use a shadow IT, such as co-workers, professional workmates, and employees from other departments, suggesting a broader range of social influence that can affect the use of shadow IT. We aid to clarify some reasons why employee uses shadow IT and how the dissemination process occurs among users. Also, as social influence is based on communication and social interactions, organizations may pay attention in creating initiatives and taking actions to engaged users in the information security policies, which is one of the primary concern related to shadow IT.