Have you ever received a “led car bulbs” related comment on your blog?
You could stop this by adding a captcha or just by disabling the comments. Unfortunately, this won’t solve the fact that you are receiving bots traffic.
Let’s say you are running a lead gen campaign, and 50% if your traffic is coming from bots; it means your server costs are double (or you can cut them by half.) Furthermore -and to me, this is the real problem- your user tracking tools are giving you false data about user activities.
It won’t fix the problem, but it is a step in the right direction: once you’ve detected from where the bots are coming from, you can start adding security measures like blocking domains.