Hacked Spam - 05/10/2015
From the Google blog:
Google have been recently implementing a number of algorithmic changes to address hacked spam in the search results. A high number of legitimate websites are targeted by spammers and are used to engage in abusive behaviour. Typically this includes promotion of traffic to low quality websites, downloads of malware, porn and the marketing of counterfeit goods or illegal pharmaceutical drugs to name a few.
Websites that do not put in place suitable best practices in terms of security can leave their websites being vulnerable to hackers. This can include government websites, universities, small business and company websites, restaurants, conferences and hobby organizations. Cyber criminals and spammers intentionally seek out these types of websites and inject web pages with malicious content to gain rankings and traffic in search engines.
Consequently, Google are aggressively targeting hacked spam in order to safeguard webmasters and users.
It is estimated that the algorithmic changes will affect approximately 5% of queries depending on the language.
As a result, if your website exists in any hacked spam keyword niches but your site is a legitimate one, you could benefit form the SERPs 'de-cluttering' which will be favourable for your site. This will leave you in a much stronger position.