recently some of our clients have reports some erronous backlinks showing in their backlinks, they think they never had backlinks from those bad neighbourhood sites but still those sites appear in backlinks,

Immediately we jumped into research and found out that there are many other people seeing the same problem,

This member in webmasterworld.com has reported the same problem faced by some of our clients

he says

"
I am getting referrals in my logs from extremely explicit websites.
I visit the URL in the log and it brings me to a totally pornographic page with absolutely no links to my site. I have however found a few of these pages cached in Google, and they start out linking to a bunch of legitimate sites, then throw up porn once the pages get indexed.
What is the purpose of this, and what benefit can come of it for the publisher.
How can I block referrals from these domains? Will receiving referrals from domains of this nature cause G to assume my site is somehow related?
"