A best solution to prevent spammers from commenting is to have a CAPTCHA or Math-based verification as spam bots fail to pass through the verification. A simple solution would be a math-based verification wherein a commenter is asked only to answer simple math questions. Here's a post on how to prevent spammers from posting on your blog.

... just a clearer interpretation of what has been in place for the last 3+ years. Comment Policy Update: Nov 13th 2009 Keywords Etc Looks like Friday 13th is a very bad day for comment spammers… No more keywords within anchor lext in the comment fieldsNo sig links under commentsHighly relevant links in the body of a comment can contain anchor text such as the blog title but they will be judged ...

... ;t got the money to pay for, and given our intelligence to resist such scams anyway, what are these spammers doing on social networking sites that have a dumber and more gullible population?  ... death-of-a-thousand-nibbles is actually a very appropriate punishment – that’s what the spammers and scammers are doing to the internet, the thing that is critical to the world economy. Yet ...

... of people and pass the real human test without trying Most validated uses on TrueTwit will become spammers What this means, is that if you sign up for TrueTwit, your list of “validated followers” would consist of a few people who REALLY want to follow you, and a swarm of spammers who signed up for the service just so they can avoid the Captcha test. In that sense, ...

... to better blogging. Bloggers who are unwilling to face reality either quite or eventually become spammers, scrapers, or beggars. I am not going to address the problem of bloggers who beg for help ... use your work disrespectfully to help them. Stopping Spam The easiest way to stop spammers who are trying to get you to link to their blog/site is by controlling your comments and trackbacks. Although ...

... PDA” notified me for new readers who is / are commenting on my blog. But, what is annoying, most of these spammers are just a pain in the neck! They don’t know where to stop and they never gave other readers ... script and make it synchronize! 3.] Next, you will need to block hackers and spammers from looking at your text file. All you need to do is add this script – straight ...