Yesterday I checked WMT for one of my websites and noticed the 'incoming links' had shot up from around 50 to over 10000. Since the feature to download latest links on WMT takes around a week to update I don't have any idea where these links could be coming from. I've checked other backlink checkers like ahrefs and majestic, but they haven't discovered any of these mysterious links. Since it's shot up by such a huge amount in such a short amount of time, my best guess is it's some kind of sitewide link, but over 10000 seems a little excessive. The other guess is it is negative SEO, but I find it difficult to believe this site would be targeted when it is quite new and not ranking on the first or second pages for any good keywords. Has anyone experienced something similar, or have a better idea of what's going on here?