Comment & Ping Back Spam in User Blogs.

Hey folks!

This is the first time i am posting after i took membership around two months ago. and i still feel i am a n00b in wpmu.

The issue i am facing is that users are facing lots of trouble due to the comment and ping back spam. and they complain that they receive around 10 mails asking to moderate the comments. they now say that i am spamming

Hope someone can help me with this issue. help is much appreciated.

Thanks in advance.

Kind Regards,
Eldo.