This study applies social contract theory to examine whether perceptions of a social contract explains adaptive behavior to safeguard online privacy. We (1) identify and (2) estimate the prevalence of subgroups that differ in their perceived "social contract" (based on privacy concerns, trust, and risk), and (3) measure how this perceived social contract affects adaptive online behavior. Using a representative two-wave panel survey (N = 1,222), we distinguished five subgroups of internet users; the highly-concerned, wary, ambivalent, neutral (the largest group), and carefree users. The former three were more likely to adapt their behavior than the latter two subgroups. We argue that the implied social contract represents an important construct that helps to identify whether individuals engage in privacy protection behavior.