I wonder though if you could simply just block the Google crawler and bypass it. Or use a JavaScript to auto-POST something before the file gets sent for download. The Google crawler doesn't issue POST requests as far as I know.
> Google Drive scans a file for viruses before the file is downloaded or shared. If a virus is detected, users cannot convert the infected file to a Google Doc, Sheet, or Slide, and they'll receive a warning if they attempt these operations.
So at least some degree of automated moderation is going on. Frankly, I'd be astounded if some amount of scanning isn't being done for illegal content and/or phishing stuff.
You can't rely on the good faith of users, if your service is easily usable for crime, it will be used for it.
I had a client wanting to defer identity validation on a two-sided market system. I had to explain how it would be used for money laundering. It had never occurred to the client.
Couple years ago got a DM from an ex-colleague and security researcher who discovered child porn that was publicly accessible. he contacted Dropbox several times over the course of 3 weeks. Weeks later the links were still up. I reached out to somebody I knew at Dropbox who said they were reluctant to do me this favor and deal with that matter and would prefer if I continue contacting their security. I continued trying on LinkedIn and contacted several people in Germany and the UK. No response other than "thank you for your email". The head of security in Germany even blocked me for saying "there is child porn on the site please help me get hold of somebody in charge". Getting really fed up by then, I contacted sales from my company email (a fortune 500 company) and asked them to give me a quote for what looked to them like a multi million $ client. Within 2 hours I got a call from the VP of sales to talk about my "storage needs". I told them about the child porn and that they are helping to actively distribute it now since several weeks. One of the videos was a girl not older than 7 getting raped and tortured. It took another 3 days to take down the material.
Yeah that must be great to walk around with...
Maybe not a great idea. In some places, that puts you in possession, and is enough for prison time, regardless of your motives.
I have done work for lawyers in exactly this scenario. Be very very careful.
You do not want to have to explain to explain the provenance of such a file without having someone to back you up.