First thing, i DON'T have facebook. At all. Stalker profile i had for EXs of mine, or friends who turned into faqers was deleted from me, some time ago. Yet while i randomly surf throughout the internet with my browser (chrome), my new strong anti-virus not only blocks various "interferences", but also catch their names (of the "services" involved) and displays it for me.

I get various reports of "Social Networks" like "ShareThis" and "facebook" actively meddling with my browsing sessions or webpages visits, webpages totally irrelevant to said social media, of course. I get reports from kommoona meddling, web analytics like "New Relic", Ad agencies like "FACEBOOK CUSTOM AUDIENCES" or web-beacons, of which i already asked about and discussed...

What the hell is this? Just what the hell is facebook's business in my use of the internet, without even having or maintaining a profile on facebook myself? And what the hell is that facebook custom audiences?

Also another question: Is it possible that i have a data leak and my internet usage being "written" on a facebook profile somewhere else?

Have you seen the "Share this" button on webpages? That is most likely what is triggering the facebook alert on your new strong anti-virus.

For more info, start reading here.

If you use Firefox, you could try a Plug-In like Privacy Badger.

And yes, we live in times where Facebook tracks without you having a Facebook profile. Although they use some sort of browser/hardware fingerprint if I remember it right.

As jmich has stated. You can get things to block all that, make sure you have noscript adblocker etc. Get some anti-social plugins going and you will be fine.

There's also NoScript, where by default scripts from facebook are blocked, and you can even mark them untrusted. Ninja'd i see..

O_O

It's just tracking analytics.

A Facebook Custom Audience is a way to advertise on Facebook to a specific audience (in this case presumably those who have visited your website). So after visiting XYZ companies website, when you go back on Facebook there ads may pop up on the sidebar or in your feed (possibly with a message suggesting you visit the site again or a carousel of products you looked at)

Also, as mentioned, any page with a 'Like' button or Share button will have all sorts of scripts and analytics going too.