Rob Schley just posted some interesting news at the main Joomla dev blog:
"During what is called the ìDeface Realtime Compoî Competition up to 150 Security Specialists, hackers, and crackers bomarded the CMS with attacks for 2 days straight without success. Both Joomla! and PHP-Nuke were evaluated during the competition and both systems received positive evaluations. Along with the positive evaluation, we received a certification from the WebSecure Group, declaring that Joomla! was reliable and recommended for use."
Its good to know that 150 hackers can't break into Joomla after two straight days. You can read more about it and the associated forum post on the Joomla dev blog.