Since the use of internet has been identified as a necessity in today’s world, businesses benefit from different aspects of this technology especially for marketing and advertisements so that the owners of businesses are searching for effective high speed and low costs ways of marketing such as viral marketing. Despite of its high efficiency and effectiveness, viral marketing creates various ethical challenges and problems for the organizations and individuals. These challenges and problems need to be noticed by the organizations and individuals. Although ethics is an important factor in terms of attracting, maintaining and obtaining the customers’ trust, many businesses using viral marketing ignore ethics. Having a brief review of ethical issues in marketing, the study deals with analyzing ethics in viral marketing in particular and describes ethical challenges of viral marketing in order to propose strategies to remove or decrease them.