Matt Cutts talked about unnatural links pointing to your site in 2012 & 2013 youtube videos. In one of those videos, he mentions that when Google detects unnatural links to a website it sends the webmaster a warning by email. Those unnatural links could be spammy links, keyword stuffing in a widget, hidden links. Thus, you are informed if some links pointing to your website are an issue. In the video, Matt Cutts reports that only 10 websites per day receive this warning about unnatural links. Compared to the number of websites on the Internet it is a very small number.
He advises using the disavow tool, to disavow inbound links that are problems. Quite interestingly the disavow tool has no link in the menu of Google search console. This means that the “disavowing links” module is not very important to Google. I have never seen any situations where backlinks could hurt another website rank in