The development of web 2.0 technology has resulted in an increase in internet sharing. The scope of this study is social networking, which is one of the web 2.0 tools most heavily used by internet users. In this paper, the unethical behaviours that preservice teachers encounter on social networks and the ways to deal with these problems are examined. A form consisting of open ended questions was given to preservice teachers. The form was developed by researchers who have studied the subject. By the end of the study, it was understood that 89% of the preservice teachers encountered inappropriate behaviours such as profanity, insults, sexually explicit photograph sharing, threats, unwanted video ads (advertisements) and verbal harassment. The results showed that teachers try to solve these issues by strengthening their privacy settings, reporting or blocking harassers, and that they also tend to share personal information only with friends and family. The preservice teachers stated that the most important unethical behaviours they came across on social networks were explicit content and personal information sharing. Teachers and preservice teachers ought to be informed about equality, respect to other opinions, human rights, personal privacy, media ethics and universal moralities with regard to online and social media content. Thus, it will be possible for them to inspire their students regarding the above mentioned values and contribute to the solution of the problems.