Google CAPTCHA breakage leads to increase in spam

MessageLabs Intelligence report for February 2008 reports that ” 4.6% of all spam originates from the major web mail-based services and the proportion of spam from Google increased two-fold from 1.3% in January to 2.6% in February.”
They speculate that this increase in Google spam occurred because hackers have recently compromise Google’s CAPTCHA. A CAPTCHA is used to prevent automated account registrations by spam bots. Yahoo and Hotmail’s CAPTCHA method was previously compromised.
Mail from the major webmail services (Google, Yahoo, and Hotmail) are from legitimate servers, and domain key signed or have a SPF record. A spam filter then can only act on the content of the message and not the reputation of the sender.
Spammers are in it for the money and they aren’t going to slow their attack. Webmail providers need to continue to work to be good Internet citizens and prevent their servers from being part of the problem.