Network cameras can be classified into indoor use only and both indoor and outdoor use. Outdoor network cameras often have an auto iris lens to regulate the amount of light the image sensor is exposed to. An outdoor camera will also require an external, protective housing unless the camera design already incorporates a protective enclosure. Housings are also available for indoor cameras that require protection from harsh environments such as dust and humidity, and from vandalism or tampering. In some camera designs, vandal and tamper-proof features are already built-in and no external housing is required.