After a brutal crackdown on anti-government protests that left thousands dead, Iranian authorities are taking the next step to crush dissent: mass arrests. Tens of thousands of people were arrested during the nationwide unrest, and security forces are still tracking down and detaining people they believe attended protests that called for an end to theocratic rule, according to human rights observers. But in recent weeks, authorities have also targeted specific groups perceived as threats to the regime, including reformist politicians, doctors, lawyers and journalists, rights groups say. The arrests have not squashed the anti-government sentiment: Protests have broken out on a number of university campuses in recent days, according to state media and videos circulating on social media. “What they have left is guns, prisons and the revolutionary courts.…