When it comes to cheese, there are a few tell-tale signs that signify that it has gone bad. The first is appearance - if the cheese is moldy or has changed color, it is probably spoiled. Another indication of spoilage is smell - if the cheese smells sour or unpleasant, it has likely gone bad. Finally, texture can also be an indicator of spoilage - if the cheese is hard and crumbly, it is probably past its prime. If you notice any of these signs, it's best to throw out the cheese and buy fresh.