There is a problem that you are also very interested in SEO: How to avoid bad links that point to your website from others.
There are many ways to block Web sites, however there is a quite effective way to tell Google that the link is not which you want by using the function Disallow Link.
First you determine which links can harm your website. The easiest way is to Google Webmaster Tool -> website -> select traffic -> choose links to your website. Then search in the list of links that Google provides, see the link does no good or may be detrimental to your website, save as simple text file. Example we name the file Disallow.txt. In the file each line saves a link. You can use the # symbol to describe the notes. For example:
Your next step is to use the Disallow Tool: https://www.google.com/webmasters/tools/disavow-links-main. Then select the website you want to prevent bad link -> clicking Disallow LINKS.
Continue confirm Disallow LINKS
Then choose a simple text file that you created as part of the article mentioned. After you submit the file, you will notice a table as follows:
If you want to edit you download the file, edit and upload it again. Note that the maximum size of file is 2MB.
Click Done to complete.
Wish you success.