The term "human rights defender" or "human rights activist" refers to a person who works to promote or preserve human rights, either alone or in collaboration with others. These people may include journalists, environmentalists, whistle-blowers, trade unionists, attorneys, teachers, housing activists, and others who are working on their own. Defenders of human rights may do so as part of their work duties, or as volunteers. In the course of their actions, individuals may be the target of retaliation and attacks of various sorts. These may include smear campaigns, surveillance, harassment, false accusations, arbitrary imprisonment, limitations on their right to freedom of association, and physical assaults.