go to webmasters panel ,it shows if there are anything you dont' want, then you can disavow those backlinks.
There are lots of free and paid backlink trackers that can check inbound links of your site and determine how valuable they are from an SEO prospective.
First check your webmaster tools if there any message from Google.If any unnatural sappy links which was noted by Google means just delete the back-links. or you may go with some online tools like 1) ahrefs 2) backlinkwatch enter your url in the above sites , you may see your list of back-links and check one by one whether it is Spam or relevant only Regards, Roger
For analyze the Unnatural (Spam) link try Google's Disavow tools. Through this you can identify the links (it is natural or unnatural).
1. Check all the backlinks in webmaster or there is so many other free backlink checkers tool. And if you want to remove those links 2. Use Disavow tool https://support.google.com/webmasters/answer/2648487?hl=en
Try ahrefs.com to check out your backlinks. I am using it since 2 years and it works charm while Google webmaster tools is a great option too.