What is Negative SEO?
Negative SEO in basic terms is when someone takes steps to try and harm your sites search rankings. It can severely impact your organic traffic or even potentially take your website offline.
Types of Negative SEO
There are actually lots of tactics people use to carry out negative SEO. It can be anything from hacking into your site and editing your robot.txt file, reporting your site as spam or Google bowling, pointing lots of questionable low quality bought links to your site from places like Fiverr or link networks.
What can you do to prevent it?
1) Conduct a backlink audit – you can get these from the Googles webmaster tool, and Open Site Explorer
2) Use the disavow tool - If you have found a large amount of spammy links
3) Make sure you are using Googles webmaster tools – Check for any messages from Google telling you about unnatural links are pointing to your site
4) Check your analytics software for any major spikes in traffic, bounce rates, you may want to set up an custom alert for this.
5) Create high quality content for your target audience first and search engines second.
6) Check for duplicate content – your site may have been scraped of content and published on various spammy sites.
Resources:
http://googlewebmastercentral.blogspot.ie/2012/10/a-new-tool-to-disavow-links.html
Disavow tool - https://www.google.com/webmasters/tools/disavow-links-main?pli=1
Open site Explorer - http://www.opensiteexplorer.org/