Why are the added Spam Blacklisted Words and IP Addresses Still Allowing for More Incoming Comments

On one particular WordPress site all of a sudden it began receiving an onslaught of spam comments (roughly 10-15 daily). Previous to this is would receive perhaps 2-4 spam comments daily.

I began going through and taking note of keywords and phrases to add to the WordPress Discussion Setting Blacklist along with a few main culprits IP Addresses that were producing the bulk of the spam.

After about a few weeks of logging this information, I added the details to the Comment Blacklist section making certain to adhere by their specifications of only adding one keyword or IP per line, but yet the website is still continuing to get incoming spam from the same IP Addresses and using the same words that I have added to the Blacklist box?

Any thoughts of why these keywords and IP Addresses aren't actually being blocked and automatically marked as SPAM?

Thanks,
Jeremy