Ahh, you gotta love Serendipity.
I just got hit by comment spam, almost 50 comments – all with different IP addresses and different bodies (if they had all had the same body or same IP, they would have been rejected by the Spam Protector plugin). Anyway – it took me only a few seconds to clean up the attack with the comment management, introduced in Serendipity v.0.7. Just click “Invert selection” and “Delete selected comments” a few times and BLING, it’s all clean again :)