https://guide.jinbo.net/workplacesurveillance/2%ec%9e%a5-%eb%85%b8%eb%8f%99%ea%b0%90%ec%8b%9c-%ea%b4%80%eb%a0%a8-%eb%b2%95%ec%a0%9c/7-%ea%b7%bc%eb%a1%9c%ea%b8%b0%ec%a4%80%eb%b2%95/