I have been seeing traffic in my analytics from adnxs.com. This appears to be some kind of ad server run by AppNexus. I'm not sure why I'm seeing traffic from here because I don't do any advertising through AppNexus.
When I google for adnxs there appears to be some kind of browser redirect virus associated with it
The traffic that comes from there is pretty bad quality, with almost no engagement. (low pages/visit, conversion etc.)
Any idea what this traffic is and if I should be worried about it?
Shouldn't and don't are two different things. It's been reported by some advocacy groups that Google Chrome does indeed send packets of data even though they publicly claim that it does not.
4.2 Google is constantly innovating in order to provide the best possible experience for its users. You acknowledge and agree that the form and nature of the Services which Google provides may change from time to time without prior notice to you.