When Spammers Attack?

Gothmolly asks: "After reading the recent spate of spam and anti-spam articles here on Slashdot, I decided to beef up the anti-spam security on my own domain. I run my own domain and mail server, running Qmail, along with rblsmptd. Mail that passes this gets hit with Spamassassin However, one particular spamhaus, Clickformail has particularly nasty servers, they try at least 2 SMTP connects/second, and I suspect that's only limited by my 384k DSL pipe. The impact on my box was non-zero, to say the least. I ended up putting a packet filter on their class C netblock to stop the barrage of log messages and increase in load (from 0.05 normal to 0.15). Has anyone else experienced such determined spammers, and what is the best way around it?"