Vigilantes in Iran
Vigilantes or Plainclothesmen (Lebas-shakhsi) in the Islamic Republic of Iran have been called "a prominent part" of the "crackdowns" by the regime on the repeated political protests during the twenty first century in Iran. Men wearing street clothes who appear to be unexceptional civilians but beat protesters, have been called "arguably the most feared and hated" of the forces deployed by the government against protesters.
Vigilantes/plainclothesmen have been described as a "third" strand in Iran's political system (the first being the formal government of president, parliament, etc., and the second being the "revolutionary institutions" of the Supreme Leader, etc.); and as operatives in "an informal but highly organized network of volunteers" that are a "powerful tool" for suppressing dissent with "both a strong ideological and financial interest in maintaining the status quo in Iran".
Attacks by the vigilantes are often in tandem with police. While often more brutal than the police, they are putatively pious civilians outraged at the godlessness of the protestors and spontaneously taking action, attacking protesters before police, and then melting away "as quickly as they appeared" when police arrive.
Plainclothes attackers may also be from security agencies (who do not identify themselves), rather than civilian vigilantes. For these attackers, plainclothes dress has the advantage of anonymity, leaving protesters and public guessing who is beating and shooting demonstrators, and when public anger over brutality escalates, allowing the government to plausibly deny responsibility, maintaining vigilantes were at fault. However, as their attacks become systematic and the police are seen to invariably stand aside during the beatings, plainclothes action undermines the government's line that they are upholding law and order, and can even lead to public doubt about the legitimacy of legal structure of the state in general.
Vigilantes/plainclothesmen are often members of Iranian "pressure groups" (guruh-i fishar) such as the Ansar-e Hezbollah (the "semi-official quasi-clandestine organization of a paramilitary character that performs vigilante duties"). Other sources state that they come primarily from the Basij (Iran International); or from the ranks of both the Basij and Islamic Revolutionary Guard Corps (RFERL); or "could be affiliated with" any of the many Iranian military and intelligence organizations; or that there are two sorts of attackers in plainclothes -- "plainclothes" who are affiliated with intelligence and military organizations, and civilian "volunteers" who are vigilantes (Maryam Sinaee of Iran International).