The thing that stinks about akismet is it costs money
Yes, i almost forget about that, that makes it kind of useless. An alternative could be the Google Safe Browsing API it checks the posted links against a white & blacklist.
Spammers always post links, the api help to block the complete posting.
I'll have to check that out for sure :)
After some testing with the google safe browsing API, i noticed it filter only phishing and malware sites as links. But all the Links posted by Spammers are not filtered. http://blogspam.net/
I added it directly to yaf. Every Post is now checked for SPAM (Detection based on Post, IP, and Name) - Of course this can be turned off/on in the Host Settings.
Currently the messages containing spam are rejected, but i think suspending the user would be also a possibility.
Also i Added "Report as SPAM" Button to an Reported Message on the Report Messages Page - that sends the Message to the BlogSpam Service.