Spam from old guestbook file won't stop

I have recently upgraded to 7 from 6.1, unfortunitly the site had a lot of spam issues because of the guestbook file now that it is gone the spam robots are still trying to use it, so I am receiving over 1000 emails a day from the system telling me that it has blocked the attempt, my question is how can I stop this? I can't keep adding the IP's to the block list there are far to many.

Any ideas on what I can do would?

This is what I am receiving:

Impact: 21 | Tags: xss, csrf
Description: finds html breaking injections including whitespace attacks | Tags: xss, csrf | ID: 1
Description: finds attribute breaking injections including whitespace attacks | Tags: xss, csrf | ID: 2
Description: Detects self-executing JavaScript functions | Tags: xss, csrf | ID: 8
Description: Detects possible event handlers | Tags: xss, csrf | ID: 32
Description: Detects obfuscated script tags and XML wrapped HTML | Tags: xss | ID: 33
Centrifuge detection data Threshold: --- Ratio: --- Converted: (((++:
Quote · 16 Jan 2010
 
 
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