Cybersex is the use of the Internet and its services to achieve sexual arousal and pleasure. This use, however, can become excessive and uncontrolled. Common consequences of a problematic engagement in online sexual activities are the deterioration of real-life romantic relationships and the occurrence of sexual dysfunctions, even in young population. Here, a simplistic mathematical model based on differential equations is proposed to investigate the impact of cybersex on the human population growth. This model is analysed from a dynamical system theory perspective. This study can be presented in a class on differential equations and it can be the starting point for talking about Internet sex addiction.