Don't shift your focus on worrying about the bad links to your site. You should place your focus on creating more links that have a higher value that those backlinks. I know this would be something that's a bit old, but if kicking a site out of the search result rankings was that easy, a lot of people would have been doing that ever since just for them to go to the top. Google's Matt Cutts has supported this in a video. I forgot which one that was about, but he said that they made it hard for the competitors to hurt another competitor.
About the Penguin update, it's best if you're going to focus more on the content creation rather than the link building itself. Yes, you can still build links, but it's a lot better if you're going to think of the people more than how your site will increase its rankings on Google's search results page.