Google has made some serious updates to the quality guidelines for sneaky redirects by including examples to illustrate redirect related violations. It has also updated the hacked content guidelines to include redirects on compromised websites.
In Google's own words, redirecting is the act of sending a visitor to a different URL than the one they initially requested and hacking is placing content on your site without your permission as a result of vulnerabilities in your site’s security.
Google posted in the Webmaster Central blog that although redirects are a normal part of how the web operates, some redirects trick the search engines and show different content to users than to search engine crawlers. Google says this is a violation of the Google Webmaster Guidelines. When a redirect is used in this way, a search engine might index the original page while users are taken to the redirect page.
This practice is misleading because it shows different content to users and to Googlebot, and takes the searcher somewhere else than where they wanted to go. Another example of sneaky redirect is when desktop users receive a normal page, while mobile users are redirected to a completely different spam domain.
Illustrating the examples of hacked content, Google said hacking includes injecting malicious content into existing pages on the website, adding new pages to a website that contain spammy or malicious content, adding hidden links or hidden text to a page by using CSS or HTML and injecting malicious code to a website that redirects some users to harmful or spammy pages.
Google confirmed that in case of any violation to the quality guidelines, it can take manual action, like removal of the site from Google index, so that the quality of the search results is maintained.Google Updates Quality Guidelines for Sneaky Redirects and Hacked Content!,