First, register the website with Google Webmaster Tools (GWT) - http://www.google.com/webmasters/tools/
Then use Google's disavow links tool to tell Google you don't want them to take any notice of the spammy links to your site.
The tool - https://www.google.com/webmasters/tools/disavow-links-main
A help page about disavowing links - https://support.google.com/webmasters/answer/2648487?hl=en
Note that you can add comments in to the disavow file, mention in there that you have no idea who set the links up or why.
First, register the website with Google Webmaster Tools (GWT) - http://www.google.com/webmasters/tools/
Then use Google's disavow links tool to tell Google you don't want them to take any notice of the spammy links to your site.
The tool - https://www.google.com/webmasters/tools/disavow-links-main
A help page about disavowing links - https://support.google.com/webmasters/answer/2648487?hl=en
Note that you can add comments in to the disavow file, mention in there that you have no idea who set the links up or why.