In blender or food processor, place chiles, onion, garlic and beans. Cover; blend on medium-high speed, stopping blender occasionally to scrape sides, until almost smooth.
Spoon dip into 1 1/2-quart saucepan. Stir in yogurt, cumin and salt. Heat over medium heat, stirring frequently, until hot. Place in serving bowl. Serve hot or cold with chips or crackers.