After April 2012, Google Penguin changed the way we do SEO and link building. Even more changes came with the last update which made Penguin 4.0 part of Google’s Core Algorithm. Penguin 4.0 can detect changes in your backlink profile with every re-crawl. This means that you need to look at your backlink profile on a regular basis. You have to find and disavow all the bad links and make Google take notice of the links in your disavow file faster.