How to Block Google Images
To block Google’s image search, open the Web Filter / Policies / Policy / Filtering Rules / Domains and URLs and add the following regular expression:
Please note, Google regularly changes its URL search scheme so if this regular expression does not work, ask firstname.lastname@example.org to research this issue. If you are good at handling regular expresson yourself, please use https://regex101.com/ to test what needs to be blocked in the Google’s image search URL and share it with support.
How to Block Adult Content on Google Images
Google images search returns image results (thumbnails) as inline base64 encoded images in the CSS. Selectively blocking them with any URL redirector will most probably not work. Our current strategy for blocking explicit search results on Google is (assuming SSL decryption is in place):
- enforce Safe Search for Google. In this way Web Safety adds a special parameter to URL and some HTTP header to all outgoing requests to Google servers asking it to show only safe images. Unfortunately this sometimes misses quite offensive images as no Safe Search is safe enough.
- add keyword filtering to filter results of image search as it also contains some textual description of images and their original URLs that greatly improves detection rate. Some possible overblocking definitely will occur.
- add image tone detection filtering to the mix (works only for JPEGs for now and higly experimental)