Pixeldrain scans uploaded images and videos against known CSAM (Child Sexual Abuse Material) databases. Currently we are working with Project Arachnid and Stichting Offlimits.
We will periodically check every image and video file on the site against these databases. Once there is a match with one of the databases, the file will be removed from our database and the IP address and account which uploaded the file will be banned.
Technical details#
Pixeldrain scans files using the PDQ hash algorithm developed by Meta. The specific implementation we use is this one: pdqhash.
Since the hash is calculated on our own servers locally, and the hash contains no details about the image file itself, it means that user data is never shared with other parties. It’s completely private.
For video files we use ffmpeg to export all keyframes of the video file to regular jpegs. Then we calculate the PDQ hash of each frame and check them all against the database separately.
The CSAM databases are continuously updated with new material. Files on pixeldrain are scanned repeatedly so we can also catch up on later additions to the databases. On average each file is checked once every 6 days.