Yes, when I wrote custom page tracking software for a custom forum I wrote and hosted, I was parsing out User-Agent information and would actually notice malwar

Yes, when I wrote custom page tracking software for a custom forum I wrote and hosted, I was parsing out User-Agent information and would actually notice malware browser add-ons, and I'd gently post a notice at the top of my web page alerting them that they might want to run some malware scans. Security vs. privacy right there. That was a long time ago, and I don't track anything any more, but it was an interesting experiment.