Google Groups being spammed ↩

I'm getting lots of comment spam attempts for some Google Groups pages, e.g. "http://groups.google.us/group/dyt-cheaptickets";. The mentioned groups actually exist, and the spam content is being hosted by Google.

There is no "report abuse" link, so I have no idea how to tell the Google guys about this.

Also, I wonder how the spammers make it past the CAPTCHA?