Yes, the LED on the back of the camera is able to be turned off. To do this, log-in to the web interface of the camera on a supported browser (Internet Explorer, Firefox, Safari). Once logged in, click on the Setup button in the top right corner of the page.
From here, click on the Camera category on the left side, and click on the Configuration sub-category.
On the right side, you will see a list of features. The "Indicator Light" feature refers to the LED on the back of the camera. Set this to OFF from the drop down and click Save to save your settings.
The LED will now be off indefinitely.