Our e-commerce site currently has thousands of duplicate pages indexed because category listing pages with all the different filters selected are indexed. So, for example, you would see indexed: example.com/boots example.com/boots/black example.com/boots/black-size-small etc. There is a logic in place that when more than one filter is selected all the links on the page are nofollowed, but Googlebot is still getting to them, and the variations are being indexed. At this point I'd like to add 'noindex' or canonical tags to the filtered versions of the category pages, but many of these filtered pages are driving traffic. Any suggestions? Thanks!