We use web filtering. Facebook and playboy are blocked. However, every so often we will notice that filtering has failed and anything is accessible. We want to set up a PRTG test which would hiughlight that filtering has failed. An http get gives a succesful result but if I try the facebook page is actually blocked. How do we set up a sensor that monitors this and if filtering is working the access will show fail and if succesful then it means filtering has stopped?