Mention what are the characteristics of "bad links"?

1. It's On A Low-Authority Or Questionable Domain
2. It's Pointing To A Source Irrelevant To Its Content
3. It's Repeated Too Many Times On The Domain
4. It's A Part Of A Reciprocal Exchange
5. It's Embedded In Suspiciously Keyword-Matched Anchor Text
6. It's Isolated From Any Meaningful Content
7. It's A Part Of A Scheme

Bad backlinks are simply the opposite of quality ones. They come from websites that do not have quality content, are not ranked well themselves, have been penalized by Google, and do not follow Google's Webmaster Guidelines. You cannot always control who links to your website, and this can be a frustrating problem.

Links from sites that are unrelated to your sites
Links from low Page Rank and Low traffic
Links from link exchanges
Links from those sites that are not in Google index
Paid links
Link from the same anchor texts coming from multiple sites
Spammy links from blogs or articles.

The characteristics of "bad links" are. Links from sites that are unrelated to your sites