People tempt to transfer their natural needs feeling and behaviors from the off line communication to the online world. One of the most important human needs is desire for security. Emotional, physical, mental, national, social, cyber: security has various levels and meanings. Our lecture about Security on Social networks was presented to Students of Faculty of Social Science at Charles University. It covers issues connected to the cybercrime, threats and mechanism of scams, as well as privacy and security settings on Social Networks