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Are these showing up in Google Analytics? There are a number of ways that these sites can fake visits to your site to entice you to visit their site when you see them listed in website referral traffic. As Takeshi said, I would look to see if they're actually linking to your website or not. These sites probably wouldn't show up in Open Site Explorer because they're so low-quality, however I don't see these links listed in other Backlink monitoring tools, either. That leads me to think it's probably referral spam.

First of all, for the benefit of the discussion it's worth pointing out that the Googlebot will ignore the CSS code and read whatever is in those tags. Using tags like "display: none" and other similar ones will not by itself result in the Googlebot sounding the alarm.  It is sophisticated enough to recognise that many web designs use the tags for a better look at the website and UX experience. Where it might start getting angry (and you won't like it when it's angry) is when it finds links within the tags - particularly those that point to completely irrelevant webpages and/or spammy ones.  If that happens, it's quite a big no-no, as it will think you're trying to hide these links from Google for nefarious reasons.  Similarly a whole bunch of content that could be duplicate and/or is being used for keyword stuffing etc would also sound the alarm. Provided you avoid that, I wouldn't worry about using the tags, as it can be useful for a number of reasons.  Worth remembering, however, that the Googlebot will crawl and see whatever is hidden in their anyway.