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Are you absolutely sure that those links are what caused your rankings to drop?  When did the drop happen?  There was a big Panda update around May 20 that caused a lot of sites to increase or decrease in rankings and that is all about on-page content as opposed to links. Google is generally very good at simply discounting the links that come with negative SEO.  One of my own sites was hacked recently and had thousands of links pointing to it with anchors like "ugg boots" and "michael kors".  Those links showed up in ahrefs and majestic but not in Webmaster Tools.  The links did not affect my rankings.  I am pretty sure that the reason why they didn't appear in GWT is because Google was able to recognize it as an attack and just discount them.  Still, just to be sure I collected the links from ahrefs and majestic and disavowed them. I have still yet to see a credible case of negative SEO working on a site unless that site already had a really unnatural link profile to start with.