1. In small bowl stir together tomatoes, vinegar, oil and garlic. Season to taste with salt and pepper. Set aside.
2. On baking sheet arrange crackers. Slice mozzarella into 24 pieces. Top each cracker with a piece of cheese. Sprinkle some prosciutto on each. Bake at 300°F about 4 minutes or just until moisture appears on cheese.
3. Spoon tomato mixture on top of each. Serve immediately