If you are hit by Penguin update and want to monitor and want to clean detox backlinks, here is a free tool you can download:
Blam-Software
What all can be analysed via this software:
1) Backlink's IP
2) Google Page Rank
3) Alexa Rank
4) Google Cache
5) Social Count: Google+, Facebook, Twitter
6) Backlink Status: nofollow or dofollow
7) Link to your site
8) Link count : Both internal as well as external
Blam-Software
What all can be analysed via this software:
1) Backlink's IP
2) Google Page Rank
3) Alexa Rank
4) Google Cache
5) Social Count: Google+, Facebook, Twitter
6) Backlink Status: nofollow or dofollow
7) Link to your site
8) Link count : Both internal as well as external