A colleague of mine is advertising on different websiets to drive traffic to his website. He hasn’t used the campaign url builder. But when we look under campaigns we can see that the traffic is tagged up with the name of the websites. Campaign name is the name of the website.
Anyone have a explanation? 
Hi,
Matomo does also support the Google Analytics campaign URL scheme (utm_campaign parameters), so maybe these are added to the URLs linking to your site.
I do not think so. But I have to double check that. If that is not the case and they only use the url without utm parameters, then it should not end up under campaigns, right?