The increasing popularity of the Online Social Networks (OSNs)\nomenclature{$OSNs$}{Online Social Networks} has made the OSNs major targets of spammers. They aim to illegally gather private information from users and spread spam to them. In this paper, we propose a new spam campaign that includes following key steps: creating fake accounts, picking legitimate accounts, forming friendships, earning trust, and spreading spam. The unique part in our spam campaign is the process of earning trust. By using social bots, we significantly lower the cost of earning trust and make it feasible in the real world. By spreading spam at a relatively low speed, we make the life span of our fake accounts much longer than in traditional spam campaigns. This means the trust we have earned can be used multiple times instead of only one time in traditional spam campaigns. We evaluate our spam campaign by comparing it with the traditional campaign, and the comparison shows that our spam campaign is less detectable and more efficient than the traditional campaign.