Integrated webcam not working due to unsigned driver CtClsFlt.sys

My webcam does not work. Dell Webcam Central doesn't even start and Skype doesn't detect the webcam. After much troubleshooting, I have concluded that this is due to one of the webcam drivers, CtClsFlt.sys, being unsigned, with the result that Windows won't let it run. The device appears in Device Manager with a yellow caution symbol. The device status in the properties dialog box has the following message: "Windows cannot verify the digital signature for the drivers required for this device. A recent hardware or software change might have installed a file that is signed incorrectly or damaged, or that might be malicious software from an unknown source. (Code 52)" The current file comes straight from Dell. I have not been able to find a replacement anywhere. Any suggestions, please?