A competitor (my assumption) was able to get my site dropped from a top 10 spot on Google, which was held for almost 3 years. I believe this was done by posting my site's link on blackhat sites (mostly Chinese sites). When I search my site on Google, all of these sites appear on the search result with a link back to my site. These links are obviously bogus, the anchor text used are mostly names of famous celebrities, adult stars and some adult content phrases. I thought there are safeguards against this type of behavior. What can I do to undo the damage? I though backlinks could only help and not do damage? Thanks in advance.